I'm not in Fl but my mandevillas are in full sun all day here during the summer and do very well. I do water them once a day, twice a day in the heat wave that we've been having.
Karyn

I am in Jacksonville florida and have 3 madevilla vines planted in front of my porch in full sun.. They are climbing up the porch & trellis with alot a vigor they should be fine.. Just be sure they get water at least once a week or the leaves will wilt and drop off.. I fertilize once a month and they are doing great..
Good luck

Thanks for your responses. I'm excited to try them out. I think they are gorgeous. Just didn't want to be heart broken. Ladybarber101 you do leave them out all year? and one more thing what are there growing habits during the fall and winter in Florida?