I am 99% sure there was not free Wi-Fi when we were there last time, but just found this link. It says there is free Wi-Fi! I hope this is true, it will allow me to get plugged back in after 6 days of being off the grid while we are waiting for our flight.
Be careful of the site above, it's run by a guy who pretends he's the official airport site so that he can recommend his own transfer service seemingly making it appear 'official'. It's not the official site at all - this is: http://www.asur.com.mx/asur/ingles/aeropuertos/cancun/cancun.asp As for Wifi, I remember my phone found a connection but was asking for a password to connect. I didn't bother looking into it further since I have the local 3G coverage with my plan anyway.
Maybe that's why I don't remember them having free Wi-Fi. I was almost positive the only Wi-Fi was not free.
I tried to log on in may as we were stuck at the airport for 6 hours due to plane problems. No free wifi that I could find. Not sure if they had any in the restaurants though...
The VIP lounge does have free WiFi, it's not the best airport lounge in the world, but for about £20 you can have drinks and snacks in comfort and use the WiFi!(all inclusive!) Makes the holiday last a little bit longer! Food and drink at the airport is expensive!
Thanks for the responses! Who hosts the VIP lounge? Is it done by the airport or is it like one of the airlines VIP club/lounge and if so which airline?
Try this link. I do believe it is run by the airport Cancun Airport Lounges | Affordable VIP Lounge Access or just put VIP lounge Cancun airport into google! Hope you have a fabulous time!