I shall be traveling to the USA next week with my wife. We each have an unlocked European iPhone 4. We are looking into getting local USA SIM cards (obviously pre-paid) for our phones but it seems like quite a minefield. We currently also have two very simple T-Mobile phones from a previous trip which still have credit, and I guess we could use their SIMS in the iPhones instead (I have a SIM-microSIM cutter) but I have heard that T-mobile's data coverage for such iPhones is only at the EDGE speeds which are much slower than 3G. However, T-mobile have an attractive $2/day pre-paid plan which would suite us quite well.

I have tried looking into AT&T but cannot see whether they have any pre-paid rate for talk and data - their overall coverage seems much better than T-mobile and they don't have the EDGE speed problem (or so I am led to believe).

We shall be part of the time in Yellowstone, where I understand we will need Verizon CDMA phones. That means we shall have to get a couple of simple Verizon pre-paid phones. One thought that occurred to me was that if there are simple such phones for Verizon pre-pay which can create a mobile hotspot we could use them for talking and use the iPhones for data via wifi.

Does anyone know more?