The most information I could find about the wifi network at the CDMX Airport is in this press conference from July 8, 2020 where it was announced that the network would be available starting from July 13 of that year. José Merino, head of Mexico City's digital public innovation agency announced that:
Finally, the city's airport will have a free and extensive internet network, in both terminal 1 and terminal 2. It's a free service for its users; they don't have to be customers of any business, they don't have to register, they don't have to give any personal data in order to be able to visit any website, with the exception of course of sites that the businesses have identified as risky, but outside of that, the truth is that there's no restriction.
It also serves, like the rest of the city's access points that I've talked about, to enable a wifi network in case of emergency.
[my translation based in part on youtube's automated transcription]
The on-screen graphic states that the network:
- Unlimited access duration
- Without content restrictions (except "black lists")
- Bandwidth of 3/5 Mbps per user to upload and download information
- Enables an emergency wifi network (for use by first responders in case of disaster)
- Up to 8000 users simultaneously connected
As you are (apparently) not a first responder, you can not use the emergency network, but you should have no trouble using the public network. I can also confirm that I had no trouble with the public network when I used it in autumn of 2021.