Flights at this price are available as soon as tomorrow with returns available through May 1, 2019. So just before Cinco de Mayo, but don't let that stop you from booking this amazing deal. Departures are valid daily, but you'll have the best luck finding seats with midweek flights.
As an example, searching AA.com, I found seats departing DFW on Wednesday, February 13 and returning from CUN on Wednesday, February 20, 2019. Other dates are widely available for winter travel with only peak holiday travel over Christmas and New Years being blocked out.
If you've got another beach destination in mind, have a look at all of our fares to sandy and sunny Best Beach Destinations here.
Want a room with an ocean view? Here's what's available for the mentioned dates on Hotelwatchdog.