Most new cell phones that are GSM tri (900,1800,1900) or quad (850,900,1800,1900) band will work overseas. GSM is the most common network. Since you know where you are going you can check this website out to find out exactly what kind of GSM coverage you need to make sure your phone has.
http://www.gsmworld.com/roaming/gsminfo/index.shtmlIf you have a tri or quad cell phone already, you need to call your provider and have the international call block removed. This is free and usually takes a day or two for the block to be released. When overseas, you will be roaming and charged additional amount depending on what network you are on.
If you check out Vonage, you can get their phone service and take the router with you. You can plug it into any network with internet access and get your calls as if you were a home and call out just the same. NO EXTRA CHARGE! Voicemail can be retrieved from their website or sent via email. It is pretty cool, but not as convenient as having a cell phone.