Check out the Alpine Century as well, mid August. A great loop, and a very nice change from the flatter farm roads in the mid-Willamette valley that so many rides use. For the OP, I'm from OR, but now in Seattle as well. I thought the Alpine ride was worth driving down for. The Strawberry century is a nice loop as well, but typically the same day as Flying Wheels. Way fewer riders though, and not as much car traffic.