Campgrounds in San Diego, LA & San Fran for Minivan Camping

I realize now my biggest hindrance is that I am flying by the seat of my pants not having specific dates far enough out and so many of these places have told me that they are already booked, but to check back for cancellations.

FYI: Dockweilers would be ideal, but they only let you stay there if you have a vehicle that is designated as a recreational vehicle. My camper minivan does not qualify :-( Least I now know what the defining criteria is at the RV parks.

Thank you to all who responded. I am going motel.