I live in Ridgecrest and spend as much time as possible in the Sierra and Death Valley.
If you want to see the Sierra, Horseshow Meadow out of Lone Pine has superb car camping facilities - but because of the altitude (~ 10K) it will be cold.
Death Valley is a nice option - or rather, Panamint Valley. You avoid the National Park hassles, restrictions and crowds. A favorite car camping spot in Panamint Valley (a 60mi X 10+ Mi valley with approximately 13 full time residents - 12 at Panamint Springs and one caretaker at Ballarat): go through Ridgecrest and Trona into Panamint V. At the road junction for Wildrose Canyon (about 2/3rds of the way to the hgwy 190 intersection, bear left. Continue north for several miles til just past a knoll on the left and a dirt road intersection with a road sign the says “Manzinita Mine” or something similar. Turn right (east) and continue to a “T”. Turn left to the dry lake or right onto rising terrain with pull-offs and spectacular views after a couple miles.
You can car camp anywhere in Panamint Valley.
booger