WalMarting; Didn't seem to be any at first, but could be able to so from San Jose and even closer from Pittsburg, CA:
California CA Wal-Mart Store Locations
One seems to allow overnighting in:
777 Story Rd, San Jose CA 95122
Edit: After looking a little more, from San Jose, it should be ok in distance, can not say about safety of leaving the trailer at the Wal-Mart or not. 28 miles to a BART station in Fremont. Give Wal-Mart a called, ask if they allow overnighting, leaving the trailer unattended part of a day, etc. Looking at the are on google map, it does not appear spooky at all. 408-885-1142
and one in:
2203 Loveridge Road, Pittsburg CA 94565
5.2 miles from a BART
Give them a call to be sure.
We have used Half Moon Bay to camp and used Bart:
RV.Net Open Roads Forum: Parks near San Francisco
15/16 miles to a Bart Station from HMB area:
Parking At BART Stations: http://www.bart.gov/guide/parking/index.aspx
BLM, Not Sure, but doesn't seem to be any very close:
Dispersed, free, camping is allowed Field Office-wide with the exception of (1) the San Benito Mountain Research Natural Area located in the Clear Creek Management Area, and (2) the Fort Ord Public Lands Area of Critical Environemntal Concern located on the Monterey Peninsula; both areas are closed to camping.
Developed camping facilities are being built on BLM land managed by the Hollister Field Office in the Laguna Mountain and Condon Peak areas of sothern San Benito County, and there are private, state, county or local campgrounds on lands adjacent to the BLM. Campers should be aware of fire season and other restrictions which affect camping on public lands in the Hollister Field Office area.
But to know for sure, need to see where the BLM Land is located. "Dispersed, free, camping is allowed Field Office-wide....."