Depends on where you like to camp. San Diego is always a destination so reservations as far in advance as possible would be advised. Especially if you want to be near the water. Las Vegas, not so much, you have Oasis (our favorite) Sam's Town (now a KOA), a few places downtown, a few on Boulder Highway, you'll find a nice place. GrandCanyon, I'd basecamp in Williams, my favorite is Circle of Pines KOA, but there are many others. The Canyon is only an hours drive away, and the town of Williams is a friendly touristy place to camp. Yosemite, if your camping in the park you must have reservations, but there are plenty of campgrounds in the surrounding towns. KOA Maraposa/Yosemite is very nice. The Redwoods represents a long stretch along highway 101, plenty of camping all up and down the State of Calif. We really enjoyed Benbow KOA in Garberville. Very central, used to be Benbow Resorts but recently became a KOA. Still very lovely.
Happy Trails.
