"Quick! To the KOA cave, Robin!"
Seems like a thousand years ago when I lived in IB! Wa'al, it was
in the preceding millenium, at least...
Many urban areas, not only in SoCal, make it difficult to successfully stealth camp. And let's face it- Skoolies ain't particularly stealthy to begin with!
Aside from over-nighting at an amenable Y'allMart, Cracker Barrel, freeway rest area, truck stop, etc, you might have to bite the bullet and pay for a camp site.
Are there any BLM, NFS, or state/county parks at hand? Push comes to shove, you might inquire at any trailer parks in the region.