Which USA SIM when on holiday in US

redux

USA has GSM and CDMA networks, there are national and regional brands, and even with roaming agreements they don't all necessarily have extensive coverage in non-urban areas.

So it depends a bit where you will be. I'd take a look at coverage maps, or ask contacts in the places you'll be.

AT&T/Cingular and T-mobile are the national GSM brands. You'd need an unlocked tri- or quadband phone, as T-mobile uses 1900 MHz and AT&T also uses 850 MHz. There are also some interesting mvno brands, such as Tuyo (on T-mobile) which has cheap international calls.

Or you might get a cheap phone there, on either GSM or CDMA - main CDMA networks are Verizon and Sprint, Sprint also owns Virgin, and the phones are not compatible with ours.

If you'll also be receiving a lot of calls from here, you might set up cheap forwarding to your US number, or brief people how to use cheap calls providers (see MSE Callchecker). Or some of the global roaming SIMs now have a dual identity, US and IoM mobile numbers. Incoming calls on the IoM number are free, and calls to it come from some but not all UK networks inclusive minutes, i.e O2 Orange and Virgin ok, T-mobile Vodafone and 3 charge. It's possible to set up call forwarding workarounds for the latter for a few pence a minute.