Jerry, we have stayed at the Viejas Casino many times. They have a huge parking lot with security, and a food court in conjunction with a small outlet mall. It is about 50 miles from San Diego center, and is adjacent to Interstate 8. You would be dry camped, but it is a great overnight spot, and will likely be plenty cool so you won't need A/C. I believe their website is Viejas.com for a location. You will have a big climb coming out of the ElCentro area, and a long downhill towards the casino.
Steve & Rhonda Bennett
Dana Point, CA
92 Marathon XL40
2012 Jeep Rubicon Unlimited
Owner: California Coach Company, LLC