If you have a GSM phone that has Bluetooth and with GPRS data service and you are in a coverage area that will support the GPRS connection you can use it as the "modem" for a bluetooth enabled laptop. If you can get a local SIM with GRPS that will probably be cheaper than using a US based SIM and roaming. I roam on GRPS in Europe and Asia to sync email and the few MB of data often cost $30 to $50 a day depending on where I am.

GPRS data is typically 30kb, and in the US and India at least the GPRS data service is being upgraded to EDGE which aggregates several GPRS channels and gives a respectable 100kb. Even the base 30kb service is adequate for (slowly) surfing the web or doing email.

Bluetooth USB and PC card adapters are readily available and not that expensive.