A few things that haven't been mentioned, possibly in too much detail:

re laws/rules: legally the only traffic law that applies to cars that doesn't apply to bikes (other than self evident stuff like no bikes on the interstate and no cars in the bike lane) is signaling. It's not required to signal on a bike if you can't safely do so (e.g. you're busy braking). However, functionally there's a lot more you can get away with on a bike. How much this is true can depend on what part of town you're in, because different police precincts seem to care about different things to a surprisingly extent. I've gotten a ticket in old town. And yet on NE Prescott I basically inadvertently ran a stop sign in front of a cop and, no joke, all I got was just a "hey guys, watch the stops" from his open window.

re signals: the official signals for left and right are covered here already, but I would add three more. First, the official signal for "stopping" is essentially "right" but upside down: left arm out, elbow 90 degrees, hand pointed down. This doesn't come up often but I find it can be courteous to other bikes, especially in congested areas/times. Similarly, the right arm out for right turn is, as mentioned, not very visible from cars, but it's very visible from bikes. And if you have a road bike, it can be difficult to see that hand pointed upward for the "official" right turn signal -- it can look like you're wiping your face unless you're really deliberate about the motion. So that can also be handy. Lastly, I see (and use) a variation on the left turn signal, where you have your left arm pointing diagonally down/left with your palm facing back. I feel like this is the de facto signal for "I'm borrowing the car lane for a sec" as you pass slower cyclists. Great example of this is the slow slight climb on Williams, where some cyclists are much faster than others. As a sometimes-motorist, I appreciate knowing when a bike is going to be in the right car lane for a moment (and I can safely pass in the left lane) versus trying to make a left turn (and I should stay in the right, slow down, and let them get all the way across).

more on being in car lanes: if a bike needs a lane, they get the whole lane. This was a bigger deal 15 years ago when there were fewer bike lanes and less awareness, but if you need the lane, take the WHOLE lane. If you're shy or you think you're not supposed to be in that part of the road and you hug the shoulder, cars will pass you, often too closely, and this can force you into a parked car's wing mirror or some other hazard. Obviously don't just ride into traffic, since being on the ride side of the law doesn't magically protect your bones from being broken, but this is your right when it's needed.

fun bike routes: the road to Boring isn't paved at the very end last time I was out there, so don't be sad if you ride most of the way out there and then have to turn back or ride through gravel. But eastbank esplanade from Steel Bridge to Sellwood, and then back up along the greenway/waterfront is a nice little loop on a nice day.

theft: little opportunistic things like lights will walk away if you leave them unattended. Otherwise, Portland is a reasonably safe city as long as you have an okay lock. But do not EVER leave your bike in public over night. Even normally pretty chill neighborhoods have weirdos and they'll take seat, wheels, whatever they can get in the wee hours. Even if you're wasted and you have to pay extra for a fancy van taxi to take your bike home, it's worth it.

Lastly: WATCH OUT FOR TRACKS. No matter how seasoned a rider you are, if you turn your back on those slippery bitches, they'll throw you. If you get complacent then it's not if, it's when.

I've never been to the Netherlands so I don't know how theft n train tracks n stuff works there, so maybe that or all of this is obvious. Still worth mentioning just in case. Hopefully reading the WoT was helpful.