California has a bunch of great campgrounds. For the sake of narrowing down the list of choices, do you want to travel up the coast, or follow the mountains?
There are pretty spectacular views either way. The coast route has San Simeon and the Hearst Castle, Big Sur, Monterey Bay, Pebble Beach, the Golden Gate Bridge and San Francisco, Mur Woods and everything in between! Following the mountains can take you through Sequoia N.P., King's Canyon N.P, Yosemite N.P., historic Placerville, Sacramento, and into Napa Valley from the east.
Oh and, ho hum, there is always I-5... truckers delight! Good for making time but little to see besides the California Aquaduct.
So let us know your approximate route and then the west based members of the HTF can suggest some cool camping spots. BTW, will you want full service campgrounds, or dry camps?
While you're stopped at Alpine, you should take a side trip north to the mountain town of Julian for apple pie. Its the town specialty!