If you're still with AT&T, call them and tell them you're going out of the country (or are already out of the country, since you are), and want to use your phone with a local provider. They'll give you the unlock code, usually right over the phone, or in an email.
Worst case, Horizon Wireless can do it within 24 hours.
BBForums : HorizonWirelessOnline.com - Horizon Wireless, The World’s Cellular Repair Center ß
They're a sponsor of the site as well.