I know that my son has rode the train a couple of times from Deland to Cary without a change of trains. It was a 12 and a half hour ride, if I remember right and there is only one train each way a day.
The route is the Silver Star and checking the Amtrak site it's about 13.5 hours to Kissimmee, no train changes. Southbound gets into Kissimmee in the morning, Northbound gets into Cary in the evening.