The issue with MRTC on AA is that it is now not totally guaranteed with the changes that they have done with their aircraft as of late.
Even though Dallas may seem to be a more direct route, connecting in Dallas rather than Denver may be a lots more troublesome with a large group due to the size of the DFW operation for AA.
The flight down to Cancun will be on an A319 that has DirectTV service. I have heard that DirectTV is free on flights to Mexico since the signal is lost about an hour out from the destination, however I have not flown to Mexico on F9.
The food that I have experienced to the west coast is from Denver is a warm bagel in the morning. Returning in the afternoon, it is a bag of pretzels.
I have been flying Frontier often as of late, and enjoy their service, and the staff.