I have 2 banana trees in pots.They have not really grown since I bought them a year ago. Should I plant them in the ground or should I leave them in the pots? The pots are fairly large. I have heard if I put them in the ground they will prosper. I live in florida where the dirt is really just sand.

Bananas like a rich soil, plenty of water and good drainage. Your soil will need to be improved to get them to prosper, but in your climate they should do very well. Dig in a cubic yard of organic matter, compost if you can get it and mulch the area heavily. Aged animal manures would also be a good additive. They are really hungry plants and will take all the water and organic nutrient you can give them. Plant them out in Spring, that gives you a month or so to prep the area. Either way, they will do better in the soil than in pots.
You'll be amazed how quickly they grow once established and you may get fruit the first summer.