just to update on sim cards and mifis :)
mrsimcard: very expensive way of buying sims ALTHOUGH he sent when he said and delivered what he said.
simple mobile sim: used tmobile but uk phones dont tend to have the right frequencies to get 3g so iphone was very slow on it AND because of lack of 3g, often lost service even for calls/texts. The best deal but not the best performer.
redpocket sim: uses at&t. Better service than simple mobile, right frequencies for uk. I still found that data was very off/on
tmobile mifi: Good data service, decent speed. Easy to top up
verizon mifi: verizon are new to this prepay mifi deal but now they do it it works great! verizon seems the most reliable network around orlando/disney and the mifi gives full 4gLTE which is amazingly fast. Faster than my uk home broadband in fact. Very impressive indeed. Topping up is more difficult, verizon dont like UK credit cards, so you can either use a prepaid visa card or buy top up cards from bestbuy.
If you plan to call/text US numbers as well as use some data, I'd get the redpocket sim. It's the best all rounder.
If you're not going to make inside US calls/texts but you need data, I'd get the verizon mifi.
For most people these days, data will give you most of what you need. iphone imessage will work, whatsapp, web browsing, forums, facebook etc.