San Diego is unique in that it offers desert, beach, lake or mountain camping...so it all depends on your interest. In our much younger days, we started off tent camping and eventually moved up to a 34' motorhome.
For me, as a native San Diegan, I liked to leave the beachy areas and go fishing or hike in the mountains. So we preferred the quiet atmosphere of Cuyamaca state park (Paso picacho) - they do offer full hook up and showers as well. Its a beautiful drive in the surrounding area and the little towns such as San Ysabel (famous stop off is Dudleys bakery - you must go in dont just pass this little bakery, you cant.miss the pack parking.lot in the middle of nowhere) Julian (quaint mointain town known for their apple pie)
Others spots in the Cuyamaca area are Lake Henshaw Resort RV (near San Usabel) and William Heise County Park (near Julian) or check out Burnt Rancheria, which is also in the area - spots are large and roomy.
A favorite fishing lake campground was Lake Jennings...a tighter feel and hotter because there is lomited tree cover and dry...but great fishing and activities.
We also enjoyed camping high desert in and around Anza Borrego Desert State park (offers many many great places that are RV friendly) but this kind of campimg is atypical of non residents who think of San Diego's beaches and such.
Every year my kid sister returns to the west coast with her family to camp up north, on the beach at the San Onofre state beach...but it may be too late in the season to snag reservations...
We moved to WA state years ago (not surpisingly enough, to an area that reminded me of the Jilian/Cuyamaca/Cleveland Natl Forest area) its therefore, been many years since I camped in San Diego, however, our son goes to college in San Diego & remains true to tent camping in the Cuyamaca area for his getaways now.....it truly is a generational recreation!
I hope this helps you and not further confuse you...camping directly in San Diego will get you crowded spots on asphalt (such as the coronado strand) or Mission bay park (crowded, loud, too close) we tended to stay away from the younger music playing drinking crowd onlieu of a quiet spot to share with the sounds of nature
2012 FR Flagstaff T12SDTH
1996 Shadowcruiser Pop Up Truck Camper
1967 Newell Motorcoach
2003 Ford F150 5.4 V8 Triton Super Cab
2004 Nissan Titan LE 5.6 V8 4x4 Crew Cab