There are three terminals that make up the Cancun Airport. There is the International terminal,the FBO [Domestic] terminal and the cargo terminal. These three terminals are close together and a mini-van can taxi you back and forth between the two public terminals [Internationa FBO/Domestic]. You catch the mini-van at the FBO terminal right out the front door; there is no sign. At the International terminal you catch the van outside the main entrance and to the right a bit, there is a sign. This service is free.
If you are traveling on your own, not as part of a travel package there are taxi and bus services [from the airport] that can take you as far as Tulum.
NOTE: If you arrive late at night the bus service may only go as far as Playa del Carmen. To go further you may need to take a taxi from the airport or Playa del Carmen. This only applies to people travelling on their own without prepaid transfers.
Those arriving as part of a travel package will be met at the exit of the airport terminal. In both terminals there is only one way to get out and these airport terminals are small.
You should have no problem finding your Tour Representative. They carry signs with the Tour Company they represent or your family name.
The reps speak English.
At any given moment there can be any number of tours arriving and the hustle and bustle may appear confusing. The tour reps know that you have just had a long flight and you want to get to the hotel. They will have your name on their list and they will not leave until they have found everyone.
Once you have found your tour rep or your tour rep has found you they will guide you to a bus or mini-van. Your luggage will be loaded onto the vehicle. You are then driven to the front door of your hotel. Make sure you get all your belongings off the bus. It is often purses and small handbags that are left behind.
The above applies to arrivals to Merida as well.
NOTE: Sometimes, even when you are travelling with a tour package you will be guided to a waiting van. Your luggage will be loaded and you sit in the vehicle. Then after waiting 10 or so minutes you are asked to exit and move to another vehicle. Your luggage is moved as well. Do not be concerned with this as it happens all the time and is a standard practice, just make sure your baggage is moved also.
When it comes to transportation, Mexico has one of the best bus systems in the world. Of course if it is your first time traveling to the Yucatan and you have the kids with you then you may want to use your hotel travel service while you learn the ropes and get your bearings. Every hotel/resort or cabana on the beach offers tour packages to any number of interesting places. In any of the small cities like Playa del Carmen or Cancun there are hundreds of small tour companies that provide transportation and guides. This varies from air-conditioned luxury buses stopping at 5 star restaurants to 4-wheel drive jungle jeeps with box lunches.
There are also taxis everywhere you go, even in small pueblos in the middle of nowhere. All taxi rides in Merida are around $30 pesos, regardless of how far you travel within the city. Everywhere else the driver sets the rate which he will tell you if you ask. You can bargain with taxi drivers and they will wait for you regardless of how long you stay at a certain location. The taxi will have a flat rate for waiting which you can ask up front. This is sometimes negotiable.