I forgot to mention one other option (instead of boondocking) -- the RV park at Mt. Hood Village is pretty nice. I know that is heresy, but I learned from two painful personal experiences that the campgrounds around Mt. Hood get really wild on weekends, because it is so close to Portland. The RV parks are much quieter! No generators, and the folks who go to the RV parks tend to be somewhat older. By 10 pm, everyone is asleep. Wonderful! The only problem is that when you sit outside in the evening, the chatty neighbors sometimes come talk to you. I usually don't want to talk and don't know how to get rid of these pleasant visitors.
The other problem is that many of the campgrounds near Mt. Hood are right off the highway, and it is easy to hear the trucks downshifting on the hills, all night long. The back of the RV park is very far from the highway.