Plenty of camping spots from 8 East then exit Sunrise Highway to Mount Laguna. A favorite of mine is Burnt Rancheria... close enough to the lodge, cabins and store in case you need supplies. Hking trails are adjacent and the views overlooking Anza and Salton Sea are phenomenal! Drive a few more miles and you'll see more campgrounds.
In CA-79, there's Green Valley, Paso Picacho, or if you're a Thousand Trails member, there's one next to Green Valley. Hiking trails are nearby and you have a choice between Stonewall Peak or Cuyamaca Peak to explore. Down the road, Lake Cuyamaca can be seen and there's a cafe, fishing supplies, boat rentals, cabins and very limited campground area which I really like. Waking up during sunrise overlooking the lake is quite a sight!
Primitive? Perhaps around Lake Morena (a bit more east). If you have a kayak, you can kayak camp.
I've been to quite a few campgrounds in and around SD so if you need more suggestions, just let me know.
Hope this helps!
Fred