Buckhorn (link contains directions and site details)
Buckhorn is a great campground with plenty of sites. It’s completely paved aprons but the sites are pretty close together. There is a lot of sharing of noise and space! That being said, there is a hike to Cooper Canyon falls. When I was last there, we hiked to the falls but there wasn’t much water (and the water was FREEZING!).
On the way up to Buckhorn during dry season:
The campsites are well shaded:
On the way to Cooper Canyon Falls:
Cooper Canyon falls (photo by my wife):
Nearby at Cloudburst Summit (elevation: 7,122ft) on the Angeles Crest Highway:
Horse Flats (link contains directions and site details)
I’ve been to Horse Flats campground in the Angeles National Forest a few times. It’s a great little campground (no reservations, vault toilets, complete pack in/out). The sites are well shaded and there is ample hiking nearby.
Hiking along the Rosenita Saddle:
Between Rosenita Saddle and Mt. Hillyer:
On Rosenita Saddle looking south: