I haven't heard of this new card before. Why don't you ask your bank or BS about this and get them to give you a low down on the charges ? Also, take at least two different cards with you, as back-up incase something happens to one of them.
I have travelled extensively across the States in years gone by. I have gone coast-to-coast twice and done Route 66 as well, but I have never been to Florida. It was always said that American Express travellers cheques could be used like dollar notes but never found that to be the case, especially when "off the beaten track" Anyway, there is now so many fake travellers cheques about, that I have heard that retailers are now wary about accepting them.
I still think a debit card is the best way.