Working at a Cadillac dealership in West Texas several years ago, we would see alot of rodent damage to cars kept in rural areas. They would chew hoses, wires, insulation to make room for their nests. It seemed worse in cold weather. One car came in with a red powder sprinkled all over the engine compartment. I asked the owner what this was since I didn't feel like accedentally poisoning myself. She said it was ground red pepper, the rodents would walk through it, then lick it off their feet, it would "burn" their mouths and they would run off to find water and not come back. I thought this was a novel idea to say the least, but, she claimed that it had been working for several seasons. Don't know if it will work for you, but, it's not poisonous, it's cheep, and it could give your brick that "Southwestern Feel" so many people looking for. :)
LOL
Rick

They can get in holes not much bigger than your finger. The question is why they are getting in. Coke spilled on the carpets? Mounds of dessicated french (sorry: freedom) fries between the seats? First clean it up to remove attractions and then place mothballs under the seats.

Likely sources of entry: missing rubber drain covers beneath; ventilating system; holes on firewall; door post vents; gasket tears, etc.