So I finally got a chance to go camping at San Onofre. I made reservations on reserveamerica about 6 months in advance for camp site 40.
All the camp sites are on a bluff. Camp site 40 is right next to trail 3 (of which there are 6 trails total), and a short 3 min hike down the bluff to the beach. The camp site itself is pretty much an asphalt parking space with a narrow dirt strip in front of it. You're allowed 3 cars. The camp site includes a bench and a fire pit. Nothing glamorous. At the restrooms, there are decently clean toilets and open beach style showers.
The camp site might not be so great, but the surf is amazing. After all, this is legendary San Onofre. I stayed for two nights, and surfed Friday evening, Saturday morning, Saturday afternoon, and Sunday morning. Waves were about 3-4ft on average with decently clean shape most days. On Sunday, the waves were 5-6ft and were just beautiful.