Before crossing the border into Mexico you should check the customs and immigration requirements depending on your nationality. You have get a Tourist Permit valid for 180 days at the border when entering Mexico. Because the procuderes are time consuming avoid crossing on weekends or holidays and try to be there early in the morning. You can also get the Tourist Permit at Mexican Embassies, Consulates and some Travel Agencies. Don't forget copies of your vehicle registration and title. You should buy car insurance for Mexico well in advance in the US. Some agencies also sell it at the border crossings but don't expect that this is cheap. For more details have a look at this link.

Don't worry! Driving in Mexico is absolutely safe! But due to animals and some road conditions you should avoid traveling in the dark. For some areas you should observe the travel advice provided on the Web-pages of your embassy.

Major highways today are in excellent condition, however, most of them became toll roads, which are quite expensive. Gasoline of all grades should be available throughout the country at the PEMEX stations but there is no guarantee that it really is available everywhere and everytime! To avoid any trap: Always monitor the attendent and the pump when your car is filled up.