Be careful "dipping into Mexico." There are a lot of problems with violent crime on the Mexico / U.S. border as of late. I absolutely love Mexico and think everyone should visit that country, but the stuff on the border right now is really out of control.
Sounds like a good trip, but only one caution:
Do not camp in Mexico. It simply isn't safe at this time. You will be okay to visit, just stay around the main thoroughfares. As a camper you'll be quite vulnerable.
Have a great trip.
We have found this book very helpful:
Foghorn Outdoors: California Camping: The Complete Guide to More Than 1,500 Campgrounds (Paperback)
We get them from Amazon.com used for about $6 or less and put one in each of our VW Campers.
They are accurate ratings, have phone #'s and directions, but the prices will be out of date depending on which edition you end up with.
My wife and I have found camps at the last moment using this guide many, many times.
Hope that help.
[ Edit: Edited on 06-Apr-2009, at 12:28 by vwurfari ]