The single most important fact you must understand about connecting flights is that THE AIRPORT IS NOT RESPONSIBLE for the connecting of your flights. The airline and/or airlines that you are flying with are responsible for getting you to Cancun on time to make your connecting flight. There is absolutely nothing that the airport can do to assist you with your connecting flights other than giving you the following recommendations:
Make sure that you book your flights with enough time to connect.
Remember that if you are flying to Cancun, then you most likely are coming on an international flight and MUST go through immigration and customs.
If you are connecting flights then you most likely getting on a DOMESTIC flight and must go to the domestic flights terminal.
There is a shuttle between terminals but it is not a scheduled shuttle. It goes back and forth as needed.
If you are flying in different airlines, then you must claim your luggage from your first flight and check them in on your connecting flight.
Immigration and customs DO NOT care if you have to connect flights you MUST go through the procedures as any other person.
Airline personnel may be able to assist you under special circumstances, please check with your airline if you think you will need their assistance. Please plan accordingly.
Weekends are very busy at the airport, thus give yourself enough time between flights. Weekdays are not as bad but if you are flying in during peak hours (10:00AM to 4:00PM) then you may run into some long lines at the immigration and customs booths.