Growing up in SoCal, I had thought this would be a lousy place to go camping when I would drive by on the 5 Freeway. But after I had gone with a group of friends for a weekend trip, I totally changed my mind. And here are the reasons why:

• You can't hear the freeway traffic
• The beach is uncrowded, plus every camp site has a fire ring and picnic table.
• You can set up your tent or bring your RV (some guys merely set up cots next to their cars on the asphalt and slept under the stars)
• World-renowned surfing just up the beach
• The campground offers cold outdoor showers and chemical toilets. No RV hookups are available, however, there is a RV dump-station. 
• Super long paved bike ride with no traffic which is great for the kids.
• Great surf fishing
• Unofficial nude beach is just south of the camp ground near Camp Pendleton.
• The San Onofre Nuclear Plant was closed in 2013 if that is a concern for you.