No. There are ways around, but the way it works here in Canada is you select your carrier before purchasing, and that is what it comes locked to. In America where you live however that is not the case. AT&T has exclusivity over the phone until who knows when. If you were to buy it from an Apple Retail store or online store it will come locked onto AT&T.
Now, if you buy it, you must jailbreak and unlock it for you to use it on T-Mobile. I gave up on jailbreaking a while back due to stability issues so I am not sure if you can Hacktivate them yet or not. For more info check out the Jailbreak forum here on TiPB. Many people are more than happy to help you out.
Hope it works out for you.