Hey, it's good to hear that somebody else has an android on this forum! Anyways, most android phones can be rooted and then unlocked, and depending on the phone, you could find tools that do this for you automatically.
The holy grail of Android unlocking and customizing is a site that is called XDA developers, in that site you should navigate to their forum and either look at the thread that deals with your phone or do a quick search on unlocking your model.
The instructions on some Androids could be a bit intimidating if you are a newbie, so I would suggest to do a quick Youtube search, before you embark on anything recommended by somebody at the XDA forums.
You should be very mindful of the frequency the phone worked in the US if you plan to use a data plan with an Argie carrier. I wrote a
post on my experience activating my phone in Argentina about a month ago, that could be of some help. So far the experience has been quite mixed with my carrier, some days the phone works well, some others...well lets just say I plan to update my original post when I get a chance.
I hope this helps and if you need further help, just post your question on the thread and I will answer as soon as I get a chance