Run the van up the Angeles Crest and the basin heat drops away into a boulder field of pines. You sleep at Chilao, the closest public campground to Glendale, up at 5,300 feet over Big Tujunga Canyon. Check length before you go: anything over 18 feet won't fit, and there are no hookups.
The way in is the La Cañada Flintridge on-ramp to the Angeles Crest Highway, then CA-2 northeast about 26 miles to the signed turn on the left. If the van runs longer than 18 feet, the overflow is Monte Cristo, deeper in the same forest off the Angeles Forest Highway, which takes a rig up to 30 feet.
Longer hauls from Glendale
Everything else worth the van is a longer drive. The beach nights, Leo Carrillo and the rest of the Malibu shoreline, sit west along the coast and belong to the Los Angeles campervan page. Joshua Tree is the desert run east, Yosemite the Sierra run north. For a group that needs more than a van sleeps, the California RV rentals page covers the larger rigs.