There isn't anything too close that is great, but Tahoe isn't too far away. Frank Raines is about 2 hours or so from the Bay. It's an alright place, but mostly hills and trails. No rocks. Hollister is ~2.5 hours and pretty fun for a few hours. Again it's mostly trails and hills, but nothing extremely technical. There's also Carnegie OHV. I've never been there, but I've heard it's mostly mud and man made obstacles.
Tahoe has a ton of places and will be your best bet for some more technical trails. There is a TacomaWorld Hollister meet on the 22nd. You should join if you can.
NorCal TW Hollister Day Trip: April 22nd 2012 - Tacoma World Forums