We've spent some time in the Central CA area, and have a great camping book as a reference, so maybe we could help.
When you are talking about Central CA, do you mean right around Paso Robles? Are you interested in Pismo Beach, Morro Bay, ?? Or do you want to come further north to Monterey, Big Sur, etc?
We've been to Hearst Castle a few times, wouldn't miss that. The whole area around Pismo Beach, Morro Bay, etc. is great.
There is a very reasonably priced campground in Oceano, CA (close to Pismo)
http://www.slocountyparks.com/activities/oceano.htm
but they don't take reservations. If you're going midweek, you can probably get in. I'd call about pet policies. It's pretty centrally located. Just don't stay by the dumpster, they picked up the garbage very early in the morning when we stayed there.
We stayed in Pismo a month ago and had fun driving on the beach. People park their RV's on the beach and camp there, $6 a night.
We stayed at the Pismo Coast Village RV Park. It was a little close for our tastes, and a lot of little kids running around, but a great location right on the beach.
http://www.rvbeach.com/ We stayed right by one of the playgrounds, that was a mistake. The sites at the top left of their map looked the best to me, after riding around the park on my bike a few times.
There is a State Park
http://www.parks.ca.gov/default.asp?page_id=595 "Oceano Dunes" very close to the resort we stayed at but I don't think they have sewer, just water and electric. You could probably get in there and get reservations.
There are so many things to do in that area, lots of State Parks, beaches, hiking, restaurants, piers, bike riding, etc.
Be aware that at many of the campgrounds you may be close to the train tracks, and the trains run at very late hours (you will think there is an earthquake if you aren't expecting it).
If you would like more info, just let me know. We are in Santa Cruz County.