Ovenchips, sorry I missed the May time window that you mention. Like others have said, May in Washington and Oregon can be iffy weatherwise. It will be either wonderful, or cool and rainy.

As far as Northern California, I just want to say that to me it was a spectacular ride. Yes, the roads and drivers leave a lot to be desired, especially with the comparison to Oregon fresh in mind. The guide book does a really good job of keeping you off busy highways where ever possible. But the beauty of this region!!! The giant Redwood groves are worth seeing, and many of the best have low volume roads going through them, like Avenue of the Giants between Eureka and Ligget. It seemed to me that highway 1 south of Mendicino was the worst, no shoulder in places, and traffic volume too. But I loved riding along the ocean so much in that area, when I got bothered by traffic, I'd pull over and sit on a beautiful beach for a while. The towns along this route are charming with nice people and good (very good) food in most of them.

I just wanted to throw in some positives here.