I second that last post. You'll find no problems in locating WiFi access almost anywhere in the US. Even the smallest motel has WiFi these days and most franchise outlets (restaurants, stores etc) have them too. I notice the comment about non-US credit cards; if, by that, you mean is there any problem with using a non-US card in the US, then the answer is there is no problem whatsoever - they're accepted without question in any store and you can use them to get dollars from an ATM.
Remember, if your need for a 'phone is simply to make calls, then you can use Skype on your iPad when you're in contact with a WiFi network. Your GSM/3G/iPad micro-SIM will work fine in the US too, but the roaming charges are usually very high. You can buy a pre-paid mobile broadband SIM quite easily - getting a micro SIM is slightly more difficult, but you can buy a 'cutter' that will cut a standard SIM down to a micro SIM (since the circuitry in a standard SIM sits just beneath the SIM contacts, the rest is just plastic and can be cut off without fear. Some people have even done this using kitchen scissors!).
Tim
Scotland
