I have driven Dallas to Monterrey over 50 times since 1999 and agree with Circle110 in regards to the ATM. If you have never driven to the interior of Mexico, it may be a good idea to obtain your car permit at the consulate in Dallas. Remember, the vehicle must be registered in your name and you must provide proof. There is an ATM at the vehicle permit office just across the border in Nuevo Laredo. I recommend using the bridge at the end of IH35 in Laredo. It has easy access to the permit office and the bypass around the east side of Nuevo Laredo. Monterrey is a wonderful city but is much more dangerous today than 2 years ago. If you are staying the night, plan on staying at the hotel after dark. The streets are dangerous after 8pm. A full service hotel such as the Crowne Plaza may be an option. San Luis is not very far from Monterrey. If you are stopping in San Luis for sightseeing, try the centro. I recommend staying the second night in Queretero. It is the safest city currently in the interior of Mexico along the PanAmerican HWY. It is also the cleanest city in Mexico. In the centro you will not find a cigarette butt on the ground. Amazing city!My wife and I will be driving from austin to oaxaca next week. Does anyone know if you can get both a vehicle permit and a tourist visa at the consulate in Dallas? Can you convert dollars to pesos at the consulate; or is there a bank close that you can do this? Also any ideas about which border crossing is the quickest and places to stay along the way (with secured parking). We plan on stopping in Monterrey, San Luis Potosi and Mexico City before arriving in Oaxaco. Any suggestions would be appreciated. Is it always necessary to bring everything in out of your car trunk each night?
Never leave anything in the front area of your car that can be seen.
Mexico City can be very challenging to drive in. If you have experience driving in NYC, you will have no problem with DF. The buses nudge your car out of the way at will in Mex City. Also, you can only circulate on certain days in Mex City depending on the last (or first, I don't remember) digit on your license plate otherwise you will have to pay a fine. You can find the specific information using Google and the Internet.
Good luck and enjoy a wonderful trip!