When driving in México, be aware that a 2 lane road is really a 3 lane road. Larger and slower vehicles straddle the solid yellow or white line on the side in order to allow smaller and faster vehicles to pass in the middle. A left turn signal from a vehicle straddling the yellow line normally is an indication from the driver of said vehicle that it is safe to pass. However, sometimes it means the driver is going to take a really wide left turn, so proceed with caution. Pass straddling vehicles at your own discretion. Remember often oncoming traffic uses the same 3, uh 2, lanes you do.
If an oncoming vehicle flashes its lights at you, it typically means there is an obstruction in the road ahead, like a disabled vehicle, a slow-moving tractor, or a herd of goats. Slow down.
When you see a sign with three turtle-like bumps or a car at an incline, immediately slow down. It’s an indication of topes or boyos (speed bumps) ahead and you can put your suspension system in mortal danger if you pass over them too quickly. Topes (See also The Deeper Meaning of Mexico’s Giant Speed bumps) vary in size and shape and there is no telling how big the next one will be. There are round helmet type topes, small thin line type topes, giant boulder size mountain topes and everything in between. Often the topes are not marked or the paint indicating a tope has long since worn away, so drive cautiously, especially in residential or commercial areas.
There are some roads so peppered with crosses that mark where someone has died after an accident that it is like driving through a cemetery. A large number of crosses indicates a tricky navigation area. Proceed with caution.
Cuota (toll) roads are available and take some of the risk out of driving, however, they cost quite a bit and are not necessarily shorter than the libre (freeway or what pretends to be a freeway). So most travel is along roads that once might have been goat paths, twisting and turning over hill and dale.