Once you get out of Metro LA, eastward You are in the desert. It will be cold at night, because of clear skies
Might try the Mono , Owens Lake area in the eastern sierras, April will still be [if it gets, needed snowfall that winter]
not thawed by then in more than the lower foothills of the Mountains.
Death Valley is certainly not at High altitude, quite the Opposite.
or the 49er gold rush highway stuff, lower foothills west side,
between the Stanislaus and the American river valleys ..