Everywhere in Orlando has pretty good service. I have used sprint for years now, and the only trouble I had is in certain spots in the resorts my phone wouldn't work, but if I stepped outside it was fine.
A coule side nots, if one company has good service not all of them will contrary to popular belief they do NOT piggy back off of each other as there are about 8 different frequencies. If cingulair/t-mobile works in an area there is NO guarantee sprint/verizon will as they run off of completely different technologies.
Another side note, virgin mobile is owned by virgin airlines/virgin megastore and they contract their tower service out to sprint so anywhere you have sprint service you will have vm service.
Make sure your plan covers you to be in Orlando before you go or else this could be messy!