go up the coast, and zig-zag the coastal range, tons of great GS riding, even if most of it is paved. at most you'll hit rain that time of year. have a flexible itinerary so you can hole up where ever you happen to be for a day or 3 if you happened to get smacked by a big wet, usually these alternate with weeks of nice weather. definitely try and get up to the santa cruz/san mateo/marin/sonoma/mendocino stretches of the coastal mountains.
see the pashnit website for tons of great road touring ideas. don't even think of going to Yosemite, or anywhere in the Sierra in the winter, it will be socked in solid snow with all passes but a couple major highways closed permanently until mid may/june.
Experience is what you get when you don't get what you want.