Going down, you should be fine. I would suggest checking flightaware in the days leading up to your trip to check which gates you are flying into and out of and can sort of plan your route. Traveling with JUST carry on for the return will certainly help, but it's tight and would be a challenge through ANY airport when factoring in customs/immigration. On our return from SXM last month, it took about 1.5 hours to clear in Atlanta.