I don't know if these two options were already mentioned in this thread but they're worth checking out (particularly if you're not traveling alone or don't have an unlocked phone):

http://www.tepwireless.com

http://www.xcomglobal.com

Both of these services will send you a MiFi like (mobile hotspot) device before you leave home and you'll be able to connect to their device through wifi with up to 5 devices at the same time. It can come in handy! Tep Wireless has very competitive pricing. I haven't tried them out yet though...