I've used these before (from the UK- got and topped these up with a UK debit card) and they've worked anywhere that has a MasterCard sign. Which is most places. I think that's the point, that they work like any other MasterCard?
Yep. We're from the UK and have used FairFX prepaid mastercards all over central Florida and in all the parks for several years now and have had no issues.
It works just like a normal debit card would. Only hang up is paying for petrol has to be done in the shop, not at the pump.