Around Santa Barbara: Gaviota SP, Refugio State Beach & El Capitán SB but no dump stations and Carpinteria SB nice one with long beach area dump site; Near but not too close to Malibu: Point Mugu SP also nice but small beach, Leo Carrillo SP excellent & with nice tide pools & Wi-Fi Service but small rocky beach. We stayed at Carpinteria and Point Mugu this last summer, and have stayed at Leo Carrillo and Refugio earlier years.
Closer to Malibu: Point Dume SB & Zuma County Beach seem to have some camping in or by them if memory serves, we have stopped @ Point Dume with its nice sand beach but not camped. Leo Carrillo's campground and Point Mugu Sycamore campground are in wooded canyons up from the beach areas, Mugu has some beach camping as well off a roadway parking area type. We also stayed at a State Park between Ventura
and Oxnard but can not think of its name now, it is a long walk to the beach but a nice campground, not bunched up and the beach was not really very nice.
This site might help: http://www.rvparkreviews.com/regions/California/