If you take up the challenge and go out driving in Mexico, please be careful. Not everybody obeys the laws and it is better to be safe than sorry. Always watch out at traffic lights, you might have green, but another person in a hurry may run the red light. Always look both ways, even at one-way roads.
Gasoline is available at stations throughout Mexico. It is sold in litres (3.78 liters = 1 gallon). Magna Sin (green pumps) have unleaded petrol. You can only pay in cash and there is no self service (You should give a tip to the attendants.) Most stations close around 10 pm.
The highways are modern and similar to the freeways up North. You have to 'pay as you go'. Take lots of small change so as not to hold up the traffic behind you at the toll booth, as they sometimes do not have that much cash around.
Auto insurance is a MUST, whether you are driving a rental car or your own.
On major highways you will find the "Los Angeles Verdes" (Green Angels). These government-operated pickup trucks are driven by mechanics. The service, if you need it, is free, except for parts and petrol of course!