I suppose how scary Portland for riding a bike is, depends on a number of things; what part of town you live in, what streets and infrastructure are there that are necessary to navigate, each individual rider's level of experience and bike handling ability...etc., etc. .
Downtown Portland and it's close in neighborhoods have plenty of bike lanes; these areas aren't that tough or intimidating to get around. To start, at least, it might help to stay off the main thoroughfares such as Burnside and MLK Blvd. Also, get and study a bike route specific map. Not trying to pitch any particular bike shop, but Bike Gallery is one that's likely to have some available (the Beaverton store has them): 'Portland by Bicycle', or the 'Bike There' maps.
As K'Tesh said, definitely get yourself set up with both front and back lights if you think there's a chance you'll be caught out after dusk and into the night. Even if it weren't the law to have one, and even in places where Portland streets are fairly well lit, you'd want a front light for visibility. There's road users in out part of the country as nutty as some of them probably are in Virginia, where you say you came from. That extra bit of illumination helps them see bikes.
Deciding what type light to get for the money you have to spend, can be a bit of a challenge in itself (try not be tempted by the cheapest, tiniest, dimmest lights out there)...at least it is for me.
Locate yourself someplace in town where you can observe, and/or talk to a lot of people that are riding. Not sure any more are scheduled for the season, but those Sunday Parkways would be an excellent op. There's bike clubs in town too, hosting rides that newcomers can join in on.
Your question about what the protocol is for being a respected rider, made me laugh. I suppose it depends upon who you ask. I believe that amongst the majority of road users, you'll be a respected rider if you use hand signals consistently to indicate changes in your direction of travel, and for stopping, ....and....stopping at the stop signs...slowing to a walking pace, looking at least side to side before proceeding.
After awhile when you've had a chance to see Portland riders traveling around, and if you read bikeportland's front page articles, you'll come to realize that certain people take considerable exception to complying with traffic regulations.
So, to sum the situation up...following the regulations will find you a respected rider among some road users...others will be totally miffed that you would stoop to following the regulations. You'll figure it out soon enough, and be able to decide which way you want to go for your own manner of riding.
But hey...you might do better with a gal's perspective. With a little luck, forum member lynnef might have a few ideas for you. She seems to have put in enough miles on the road to know what a cyclist might do to set up their bike in terms of basic equipment, and how to be a noble, respected cyclist. Check out her blog:
Lynne's Mostly-Cycling Blog