There are a lot of campgrounds on the East side of the SIERRA. How quiet do you want?
Mammoth Lakes RV in town of Mammoth Lakes is central to the Southern part. From Lone Pine up to Bridgeport there are literally hundreds when you consider FS, BLM, parks, resorts and campgrounds. Like it is down here in So. Cal., reservations are required anywhere with hook ups and near fishing and camp supplies. Tom's Place, Crowley, Twin Lakes, Walker Gorge/Walker area, Bridgeport all have either FS or Private parks. We always like Chris Flats in Walker Gorge but we haven't camped there since we bought a home in Mammoth Lakes in 1983.
We have never camped on the West side but friends go to Bass Lake North of Fresno every year. There are a lot of reservoirs and lakes East and North of Fresno.
Pick an area and then Google RV campgrounds in that area. Try the FS listings, BLM in Bishop has a map of areas open to boone docking or on line.
Where are you in So. Cal. area?