I grew up in sonoma county, & still visit fairly often. Most of the stuff we used to skate in the old days is gone now, sadly, but there's still some decent stuff. This spot is in Petaluma (my home town) & is always super fun:
Santa Rosa Junior College has been a pretty good spot for decades now...
Obviously, there's Novato High (famous double set).
Let me know what kind of stuff you're looking for & I'll see if I can steer ya...