i camped at point mugu about a year and a half ago, it was pretty cheap and the beach was empty. that was in october though, so i don't know how you'll fair right now. it was pretty nice though, my tent was right on the beach next to my favorite highway.

jalama beach
last time i was there it was 9-10 bucks a night. best around october,when you can get a spot on the sand. good place for surfers. far from big highways and the road to it ends at the camp site. great coast with boat wrecks. cliff swallow colonies. amtrak train goes by. lots of free firewood brought by the creek. i wish they had more public campsites on the california coast. i used to camp free of charge near mendecino in northern california. deserts are nice too,in california.
http://www.santabarbaraparks.org/DOCS/Jalama.html

second for point mugu -camping by the beach is beautiful and it's not expensive. yeah, the highway is right next to it, but the noise is actually kinda soothing with the ocean waves.

right on- both of those seem like they'd work. anyone know about any "unofficial" places to camp out around san onofre? I'll be in the area for at least a few days, and wouldn't mind saving some cash.

will definitely hit up jalama and mugu. thanks.

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also check this link