Be extremely careful when taking taxis in Mexico city. Never take the white and green taxis on the streets. Always ask the staff at your hotel to call a safe taxi for you, because it's really common that fake taxi drivers rob people, especially tourists.
When getting from the airport be sure to take the taxis sold infront of the airport entrance. But be sure to bargain the price before stepping into the taxi. They tried to charge us for 7 people when we were 3.
Avoid at all costs taking taxis on the street.
There's been really bad cases of robberies, sexual assaults, and other violent crimes (including killings) perpetrated by taxi drivers and/or accomplices. See Lonely Planet Travelers Book for Mexico for more info.
Rather, call renowned taxi firms, and ask:
-name and ID number of the taxi driver coming to pick you up
- number plate of the taxi
You can also ask someone reliable (ex: hotel clerk) to note the plate number and where you intend to go.
Taxi Radio Mex
The city’s traffic moves in a very fast pace, so be observant when crossing the streets. In Mexico City the cars and trucks seem to have the right of way rather than the pedestrians. I saw so many close calls, I was surprise that I didn’t see anyone get hit.
O80 is the number to dial in the event of an emergency.
The same principles apply in Mexico as in any other country.