You will love it up there if you can deal with the rain from Nov.-Feb. When I moved there it rained 93 out of the first 95 days I was there, but was one of the best ski years they had. I lived in Alder Creek about 20 miles from Mt. Hood for 8 years and taught snow safety/ and Mountain travel and rescue for the Mt.Hood Ski Patrol before moving back to Az. The guidebook series 100 hikes is good, but the key is planning hikes for example to waterfalls when there is good flow or hiking in Washington when the huckleberries are ripe. Hikes in Hood River/Columbia during the times of the year when your favorite fruit is in season. Also, you might want to get a guide on plants of the Northwest as there are numerous varieties of berries that are edible to be found along hikes in the area.
You are correct cotton will not work. You might check out Next Adventure when you get to Portland. They carry everything and is my favorite outdoor gear store ever. They also buy and sell used gear and have a pretty good outdoor
community. Anyway, hope that helps. I will look through my Oregon hikes when I get back to Az. and give you a couple suggestions of hikes to try and directions if you like. Then you can post triplogs and pictures so I can vicariously be transported to Oregon.