Mexico City
In the city you can easily get from A to B with one of the numerous taxis. It is advised however to take a registered one, a so called Sitio-taxi which distinguishes from others by size (bigger) and has a registration plate inside. These are somewhat more expensive than the others, however still pretty inexpensive. The subway is often a good choice because it is the quickest way to move, however often very crowded and stuffy.