I'm doing the JFK-MEX-GUA-MEX-JFK run in a couple of weeks. Leaves JFK at 3:20pm on the 787-9 with a connecting flight landing in Guatemala City at 10:50pm. Inexpensive overnight in GUA with return flight the next morning. If you want to get back to JFK on the next day, you can land at 12:25am, but I chose to take the 787-9 the following morning from MEX. I really like Mexico City and enjoy spending an evening there. It also gets you 787-9 vs. the 737-800. To me the experience on the 787-9 and the extra time in Mexico City makes an inexpensive overnight in MEX well worth it, but that's me. I'm leaving on Friday afternoon from JFK and back in NYC early afternoon on Sunday.