I live in the Northwest, and the surf sceen is all about windsurfing here. I don't know much about the Seattle area, but in Oregon (Tir in the 6th world) the Columbia river (or whatever the damn danelion eaters have renamed it) is some of the best windsurfing in the world, especially around the Hood River area. I assume there must be places to go in the Seattle area. If you google Seattle Windsurfing you get a ton of hits for shops, lessons, etc. While the water is probably somewhat nasty in the sound, I don't think its necessarily an acid bath. You are going to want a suit of some sort anyway, that water is cold and so is the wind most of the time, I am sure the 6th world windsurfers have adapted their gear to handle the environmental conditions.