Northern California - Where can I do lite MTB single track or CX riding in the Bay

I tried CX racing for the first time this year and loved it. Once the season is over, I'd still like to do more of that style riding (basically off roading with drops). Where in the East/South Bay can I find some decent trails that are light enough for my suspension free cross bike with 700X35 tires to handle, but are bumpy enough that it will really help me improve my handling skills?

In the Peninsula/South bay: Arastradero, Fremont Older, Stevens Canyon, Almaden Quicksilver, Grant Ranch, Alum Rock . To be honest, you can take a CX bike on almost anything, even single track. Okay don't try going to Soquel Demo Forest....

It might be bit out of your way, but worth it, Black Diamond Preserve, between Antioch and Clayton.

http://www.ebparks.org/parks/black_diamond

From the Clayton side, a good long climb, then many choices.

From the Antioch side, I recommend the Frederickson trailhead, go on up that little hill, take the main trail down into the valley; from there, three nice hills to pick from. Do all three!

Most of the firepaths are in good order, and are bladed early Summer each year. In the winter, the muddy sections get f'd up by the moo cows. :(

From the BART end o' the line in Pittsburg/Gun Point, the bike path to Black Diamond is flat and easy, just lots of street crossings.

Keep a sharp eye out for sticks in the path, especially the kind that start wigglin' !

The variety of rattler there has a distinct green tinge, especially right after molting.

Speakin' o' critter, there are tarantula, bobcat, cayote, deer, fox, etc., all that, and... a mountain lion! ...as well as crazed bikers and hikers.

Me miss it so.

I read on the Alice@97.3 web site that Black Diamond Mines is haunted! Boo!