<font face="Verdana, Arial, Helvetica, sans-serif" size="2">You could also buy a local pre-paid sim card for your gsm phone and use that. Rates to the us won't be much lower tho - but if you call using us issued calling card you may beat the 99c t mobile charges. And in-coming calls are usually not charged/local calls are cheap. </font>
Folks from home / colleagues won't know your phone number unless you give it to them in advance, though. I prefer the seamless nature of bringing along my every-day phone, so whoever needs to reach me can just reach me, whether they know I'm out of the country or not.