You shouldn't have any problem getting a spot at any of the State Parks on the peninsula (within 1-2 hours south of the city). They seldom fill up during the winter months. Also, rain is forecast for Saturday which should further lessen demand.
All of these State Parks are great:

Portola Redwoods:
http://www.parks.ca.gov/default.asp?page_id=539

Butano:
http://www.parks.ca.gov/default.asp?page_id=536

Big Basin:
http://www.parks.ca.gov/default.asp?page_id=540

There's also a San Mateo County Park that is in the same vicinity.
Memorial Park:
http://www.co.sanmateo.ca.us/smc/department/home/0,,5556687_12313309_12328487,00.html#Facilities

-Dave O'Shea

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Michael Diehr
Sent: Friday, February 03, 2006 3:34 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Early bird got the worm...

Can anyone recommend a vanagon-friendly campsite that is pretty
(beach or redwoods), within 2 hours of SF, that is likely to have
space and/or takes last-minute reservations? (for tomorrow, saturday
night).   I'm more familiar with southern california joshua tree, and
it's availability ebbs & flows.   Don't really want to show up
somewhere and get turned away if there's no chance of finding an
opening... thx!