I flew Mexicana from ORD-GDL their F class a few times, and every time I had no problem. First time, ORD-GDL we did get a semi-rude FA, but the flight overall was nice, food was OK (technically its still domestic flight) and luggage had no problem, even tough I had 3 carry-ons. Back was also nice, went to lounge and relaxed before the flight. The flight left/arrived on time, no problems. Last week I switched my flight from ORD-MEX to ORD-GDL as they oversold it (I volunteered. Who could pass up $600 voucher and I told em to bump me to F) which they did, and even tough it was a 2AM flight, they still had food, though it wasnt anything special, and seats were regular F seats, FAs were nice, and the person in charge of the flights that night was extremely helpful, took care of everything from rerouting the luggage, double checking it, redoing the tickets, the vouchers, etc the hole time, and didnt just tell me to go there and here.

Overall, never had any problems with MEX, I fly them a few times a year E or F.