Mexico City has a very efficient subway system which is clean and modern. The fare is inexpensive and transferring from one line to another can be done at no extra cost. The metro is currently undergoing extensive expansion. At this time, there are two Airport Metro stations. To be sure you have the right bus, state your destination in a quizzical tone and wait for a SI or NO from the driver.
Buses cover most of the city.
The sign in front of the bus indicates the final destination. Buses are entered from the front and exited through the rear door. You should have small change available for bus fare. Ring the buzzer over the back door prior to your desired stop. Try to move toward the back door a couple of blocks before your destination.