First-come, first-serve campsites in SoCal?

[joejld1]

Hi,

Any good first-come, first serve campsites in Southern California?
Preferably on the coast or a lake.

It will be for a Friday to Sunday trip, preferably in the next month.
What is the best time to go on a Friday to make sure we get a site?

I've tried ReserveAmerica already, but it looks like the ones near the coast are all reserved already until October.

Thanks

 

[FleshLight]

Crystal Cove State Park