I would definitely check street level coverage before purchasing a T-Mobile pre-paid SIM card. Cingular/AT&T wireless has better coverage, and their pay-as-you-go plans are about the same as T-Mobile. Those are the only two National GSM carriers. Otheres, like Verizon and Sprint also offer Pay-As-You-Go I believe, but they use CDMA and TDMA, so you will not be able to use your own GSM Handset.