Don (and anyone else who was thinking of taking SR-76 west from I-15), you might be better off getting on the I-15 northbound, then exiting on SR-79 South, which is the first Temecula exit, just as you come down the hill from the Border Patrol checkpoint. The signs will indicate towards Indio. Don't confuse it with the north version that intersects I-15 at Winchester Road, at the north end of Temecula. Stay on SR-79 South for about 45 miles, then turn left on to S-2. There will be signage indicating Anza Borrego, and the road only goes to the left at that T-intersection.
From there, stay on S-2 (do not turn left after 5 miles on to S-22, even though there is signage indicating Borrego Springs and the State Park Visitor Center). Stay on S-2 until it intersects SR-78 at Scissors Crossing. You'll make a right turn on to SR-78, go about 100 yards, then turn left in order to continue southbound on S-2 to the meet spot.
Don: I forget how far north you are, but there may be other routes to Temecula that are faster than driving all the way south on I-5 to SR-76. And, SR-76 has a lot of stops and traffic. Bobby and Rachel said it really sucked when they drove it in November on their way to the meet spot. You may even find it faster to take the 91 to I-15 then go south to Temecula, but I'm not sure about that. Or, maybe Ortega Highway, then south on I-15.
There are several gas stations on SR-79 South right after you get off the Interstate. After that, I think there may be one in Warner Springs but I'm not sure. After you pass Warner Springs there are no other stations that I know of along the route. There is one in downtown Borrego Springs, but we won't be over in that direction at all. It would be best to top off before leaving Temecula.