I think Kaiser is fairly inexpensive but also kind of crappy, as it's the Cal. equivalent of Group Health. If you're being paid under the table, and/or can report a very very small income (in S.D. it was $600 a month or under), you can apply for county medical assistance. It takes a while to go through, but is retroactively applied. It covers most everything.

Hope this helps. It's been a while since I've been in California.