After factoring in fuel and hotel stays along the way, you might find you have a hard timing staying within your budget. That said, I think you identified the cheapest way to do this kind of move.

You could also inquire about car shippers. The shipping charges for each car would be above $500 each, but you could ask for a discount shipping both of them. You could then drive a rental truck yourself, assuming you have a small amount of stuff. You might be able to squeeze into your budget that way.

But it sounds like you have help on your move. So maybe ship one car, drive another car, and have the other person drive the rental truck; that way you might be able to rent a smaller rental truck, and you won’t have to drive a bigger rental truck while towing a car.

Finally, ever thought about selling the car and trying to pick up a new one in San Diego? Do the math with the hassle and cost of transporting a car, and see if it's a better deal than selling your current car there, and buying new or used in San Diego.