I've been to CUN twice & both times, 2 hours was plenty of time. That said, I'm was also an elite member flying in first class - so I used the first class check-in line. If you're checking bags & won't have the ability to checkin online in advance, I'd give myself at least 2 hours. If you'll have the ability to checkin online & don't need to check bags & can just go to the gate, I think that the 1:30 is fine. I'd go with a 2-2.5 hour window - just to be safe. If you're concerned, it's better to sit & have a few drinks than to be rushed, IMHO.