dude, three words: tent tarp & sleeping bag
I have been homeless several times in California, and it's not as bad as it sounds if you stay out of the urban centers. I'd suggest staying in Marin would be your best bet.
If you can't find anyone who'll let you live in or near their yard, then bushwack, my friend.
Eat at soup kitchens and don't forget to learn how to dumpster dive ( I once ate an excellent lobster dinner, no lie). Watch out for drunks and get this: most other homeless people you meet will treat you pretty fairly. Drugs are OK, a way to pass the time, but don't overdo it.
Find out where you can take a shower.
Ask around for low level jobs, volunteering is a great way to meet people who will get to know you and will lead to paying gigs and maybe better shelter. Visit your local welfare (food stamp) agencies. Watch the skies.