San Onofre is less than 2 hours from our house, the surfing is great, and we both have fond memories of beach days there growing up. I always read reviews before I go somewhere, whether it's a restaurant or a campsite, so I knew that the bluffs campground there is basically a parking lot next to the freeway. In other words, the campsites are not mind blowing and you are very, very close to your neighbors. You shouldn't go if you're looking for a pristine wilderness experience. If, however, you are looking for prime beach access at $33/night, you are in luck. The campsites are on a bluff above the beach, so you hike down to the water and we spent every daylight hour there. You're far enough between cities that at night the stars are gorgeous and you can just pretend the freeway noise is waves (not really, but once I'm sitting in front of a campfire I'm pretty happy regardless). I don't think we'd ever do more than two days here, because the activities are pretty much limited to hanging out at the beach and they only have cold outdoor showers. But for a quick, easy getaway it was perfect.
Tip if you're traveling with a dog - only trails 1 and 6 are dog friendly and the campground is a few miles long, so make sure to choose a site that is close to one of those trails. We prefer trail 6, since it tends to have fewer people. Pay attention to the signs when you get to the beach! Dogs are allowed in one direction but not the other. They will absolutely ticket you if you have your dog in the wrong area.
Detailed PDF on the campground layout here, in case you're interested. We used this to choose our site, along with checking out the photos here. Each site has a fire ring and you can buy firewood there.
