I havnt wheeled in the Bay area since 1991, we used to wheel along a creek near Sunvalley mall in Concord a lot.
And the rare ocaissions there was snow we would wheel Mt Diablo, my backyard fence was along the park boundarys.
Stinson beach used to be a great place too. Learned how to drive the hell out of sand rails on Stinson beach back in the 70's.
There were also quite a few trails along the Sacramento Delta directly across from the moth ball fleet (south side of the river) that we used when sturgeon fishing.
Im sure most of thats changed in 24 yrs.
Down near Morgan hill area there used to be an old ghost town and off-road trail also, I went on a Military only invitational trip to the ghost town with Off-Road magazine back in 1986.