Should you find yourself operating a motor vehicle, bicycling around my fair city, walking, or merely a passenger in someone else's fashion-item-masquerading-as-capital-equipment, understanding the local road mores brings a moderate bonus in navigation efficiency, provides cultural background to silently judge fellow denizens of the asphalt, and the context to appreciate just how bad drivers in this oversized town really are.
The world is a sad and miserable place, drivers and other road-users the saddest and most miserable of even Americans. Do your part to bring cheer and happiness to the world by surprising and delighting everyone around you by gifting them your right of way should you find yourself in the unfortunate position of having it. That the "right of way" should accrue to any one person in an interaction is a pernicious artifact of the confluence of patriarchy, capitalism, and zero-sum economics: we must all band together and take care of each other, and the best way to do this is to give people the right of way unprompted and unexpectedly.
When you consider the speed limit, know that ODOT traffic engineers simply follow Federal guidance and seek to optimize on average vehicle speed through every section of road. This bit of knowledge should convince you that the speed limit is dangerously high, and ODOT doubtless at fault for more fatalities than hormone-flooded teens, heavily intoxicated Beaverton residents attempting to get home from Dirty at 2:30, and negligent vehicular homicide, firearms, and maniacs prowling malls all put together. With that in mind, you should never ever even approach the speed limit, and if traffic conditions are anything more hazardous than a completely empty road in the middle of summer with the sun to your back, 10MPH below the speed limit is likely safer. All of the above guidance is even more relevant in the sub-30MPH regime. Don't try to extrapolate some sort of percentage below the speed limit that is safe for those situations, you'll just distract yourself with the problem, run over someone's doddering grandmother, and then how will we forestall the Trumpenreich?
You will frequently see orcs, barbarians, Californians and Washingtonians violating these rules (less frequently, you'll see Canadians driving around, but they have a sixth sense for the rules in any given place and unerringly adhere, so you'll probably never observe them actually transgressing). At first, shock will course through your veins: "Did he just turn right under a red right-pointing arrow?! Doesn't he know how dangerous that is?!". Thirty seconds later, as the adrenaline spike from watching someone else break the rules in a most dangerous fashion drains from your bloodstream, leaving you a shaken, harrowed mess, you may remember that you purchased a vehicle factory-equipped with a horn, and that the opportunity to use it fast slips from your fingers. Think carefully now about honking: did the Californian commit a bona fide infraction? Could you perhaps explain his or her actions to your passengers as born of ignorance? Possibly your antagonist is simply having a bad day, and per the Universalist mandate, you should forgive them their sins because lord only knows what mistakes you made while driving today, for which other drivers forgave you, all unwitting.
If, after all of this searching to understand your and your counterparty's places in the cosmos of transit, your identity politics permit you to take the exceptionally hostile act of honking at another human being, you may lay on the horn for no longer than one and a half seconds, and you may only emit one blast like this. Remember, you are no New Yorker, relying on the primitive single-bit horn to communicate such varied information as "the light has turned green and you should probably move your ass at this point" or "hey dipshit parallel parking on Burnside during rush hour is one of the more spectacularly stupid things I've seen on my commute today", or a Cairo-born cabbie still under the delusion that the horn is a useful way to communicate that he's in your blind spot ("In this country we are civilized, sir, and check our blind spots before actuating our turn signals! What mean you by these five tenth-second beeps?!").
Under no conditions may you lay into the horn to advise people around you that some Bad Shit is about to happen. Mind your own business.
Rush hour, to return to a previously tangentially touched-upon topic, is the one time when you are allowed to become frustrated by the speed of life in Portland. At all other times, you have no business zooming around at (or above!) the speed limit. This is a small town, zhir or mrdame, and the roads not congested. Moreover, you are in no way more important than anyone else, and so your feelings of frustration at the time it's taking you to get your wife and about-to-be-born child to the hospital are entirely unfounded, unjustified, and downright elitest (you scum). Unfortunately, during rush hour, everyone else is on the road trying to get home at precisely the same pathetic crawl as yourself, and so you should really just put those feelings of put-out-ed-ness down and turn the dial over to NPR to catch the news. Besides, you get stuck in this morass every day anyways, why are you still getting bent out of shape?
Please use every bike lane for anything that comes to mind! Should you need to unload packages, the bike lane is a fantastic place to put your car while you run up and down the stairs of your unreinforced masonry building whose owner wisely decommissioned the elevator in advance of ADA regulations hitting the books to avoid having to maintain it and service handicapped tenants. Should you need to turn right (or left in some parts of town!), make sure that you rush up to your corner, pull into the bike lane, and then watch your rear view mirror until the bicyclists safely navigate around you on the side to which you are not turning, and then continue driving. This ensures that you get to the corner as quickly as possible, that you demonstrate great care for others' safety on the road, and that the greatest amount of time and space is wasted. This will feel natural for your first three years in Portland, then for another four years you'll be horrified at the sight, and then some three years later you'll stop giving a shit as you achieve traffic mastery and glide through the world quickly, confidently, and elegantly without attracting even so much as a single side-eye.
If a car a block in front of you is stopped in your lane, drive up behind them and at the last possible moment, change lanes (remembering to inspect your blind spot!) and swerve around it. This will maximize your chances of running a hapless pedestrian over. If you're lucky, you'll hit one of the children of the elite, and the rest of Portland will cheer. You should seek to swerve at just under the lethal-to-strike-pedestrians-at speed so as to maximize the healthcare costs that her family will have to bear. Do your part to reduce income inequality! Rich people don't have to buy health insurance like you and me; they have a bevy of accountants instead.
Queue aggressively. If you know that these three lanes neck down to two some four miles down the road, you must not drive in the lane that is closing from the moment you get on the highway until the moment that lane closes. Maximizing the number of cars packed onto the highway isn't your concern: your concern is to be as polite as possible, and to avoid the hassle of merging when the road actually applies pressure to do so. Only self-important assholes in Mercedes, dildos careening about in Corvettes and penis-cases on unmuffled sport bikes are so selfish as to use the empty lane on the right to pass the polite, calm, nice, right-thinking real Portland drivers who queue up in advance and voluntarily burn their own precious hours to serve the greater good.
Finally, plan your trips such that you always need to turn left across the major two-lane streets in town like Burnside, MLK and Sandy. That the two lanes of oncoming traffic are nearly fully-subscribed, that the minimum amount of time you'll have to wait for an opening is over three minutes, and that you're delaying an entire regiment of cars behind you should bother you not one whit, for you are following convention and turning left across major roads as instructed.
Should you find yourself stuck behind someone turning left like this, you are strictly forbidden from honking. That would be rude.
Bicyclists, I have guidance for you as well, but I shall keep it brief, as my child has woken up and I would like to play with him.
Firstly: thou shalt ride up Hawthorne, one of the Southeast's busiest streets without a bike lane taking up a full vehicle lane. Most riders will prefer the right lane, but I award the most points for taking up the left lane: you'll never know when a bus will be using the entire right lane to pick up and drop off, and you want to maximize the inconvenience delivered to drivers in your vicinity. Besides, per Oregon 814.430(2)(c) this is fine! There are caveats of course, but you can always feign ignorance and smash someone's windshield with your bike lock if they get in your face. In general, you should never ride through quiet, safe, low-traffic neighborhoods or along designated bike routes with no stop signs and cars routinely diverted off if you can instead make a nuisance of yourself to drivers.
Pedestrians, you're mostly all conversant with how to best operate your butts around town, but I still have a few pointers for novices.
Approach corners striding aggressively (remember, "every corner is a crosswalk", and all other traffic is required to stop for you. Even on MLK and Grand!), wait for cars to arrive at the conclusion that you intend to cross and stop for your transit across the road, and then abruptly stop to pull your phone out as though you've just received the most important text. This signals to the drivers that you don't actually intend to cross, and they can now burn a bunch of gasoline to re-energize the vehicles they just stopped for you. Do your part to make car ownership expensive and an indicator of elite status.
Remember to never jaywalk. If the walk sign is red but there are no cars, you should linger on the corner for as long as possible to get the opportunity to cross while some driver is waiting to turn left until you pass through the crosswalk. If you find yourself in the middle of a block and want to cross, walk instead to the nearest corner, wait for a car to make nervous with your presence, and then stroll casually in the right direction. Bonus points if Google Maps suddenly routes you in the opposite direction and you can turn around without checking your blind spot or where the cars around you are and want to be.
Be safe out there!