240dude,
California is a bit screwey about this (what else is new) and you have to "join" a co-op so they can presumably monitor if you have problems with the new fuel. I checked out a few places by just looking them up here:
http://www.biodiesel.org/buyingbiodiesel/distributors/showstate.asp?st=CA
You might want to check further on Google as I know there are at least a couple of stations in Berkeley that sell it but
afaik you'll still need to "join" to buy it.
The easiest one for me was Marin Biofuels in San Rafael but it looks like there are a couple in the South Pennisula that might work for you. I'm still waiting for my "fueling card" so I can fill up. I'll probably do an in-tank blend by filling up when I'm not at empty to get a tank or two at B50 or B75 to start. After that I hope to use B100 as much as possible.