We flew through Atlanta from Minneapolis last year and are again this year. Last year our TA made sure we had almost 2 hours. We didn't need it. There is a train on the lowest level that zips you to the area we needed to go. We were there in just a couple of minutes. This year we also only have about an hour. I don't think we should have any problems though.
you will have to ride the underground train between concourses
Usually, when you check-in in Mil they will know which concourse you will be landing at and which one you will be leaving from for MBJ. When you get off the plane in Atlanta head for underground transportation or baggage claim. You will descend on a long escalator and the trains come every couple minutes and everything is well marked.
Things change, so when you get off the plane in atlanta make sure that you check the departure board to make sure the Mobay departure has not changed gates
We also have a tight connection at ATL this coming December (47 minutes). I haven't flown through Atlanta since I was a child, so I've been doing a little research since we have zero room for error. I'm having nightmares of OJ Simpson and a Hertz commercial.
The international terminal is Concourse E which is the last terminal furthest away from the main terminal. Furthest east if you prefer that type of direction. This is most likely the concourse from which your Montego Bay bound flight will depart. Follow the signs to the train and Concourse E. From what I've read and heard, the transit system is very efficient and very fast. I'm hoping for the best. Also hoping that our incoming flight gates at concourse D.
Like drbcwp stated above, ask for the gate info when you check in at MKE and then double check it when you land in Atlanta.
Technically the train is called the "Automated People Mover" or "APM". I only bring this up, because I don't know how the signs are going to read.
Good luck and wish us the same. I'd hate to get stranded in Atlanta when our goal is paradise!