Other Car Rental Programs/Partners (ie. Alamo, Enterprise, Sixt) - Car Rental recommendations at SAN (San Diego)

I am planning a trip to SAN (San Diego) next month and I am not sure who to go with for my car rental. So far Enterprise has been the cheapest that I have found. I made a reservation for the Premium car which states a Nissan Maxima or similar. Is that what usually is given?

What car rental company do you think is recommended at SAN? I also plan on going to Mexico one day while I am over there. Any help would be greatly appreciated as October will be here before you know it.

Make sure the rental car company allows the car to enter Mexico. Many companies have restrictions on this.