My bad, you are correct Andrew...I was assuming that the OP was interested in buying the global version of the phone, but as you mentioned, the US version of the phone should pick HSPA+ even if his area has not been refarmed.
Re: global GSM vs US GSM version on tmobile
Maybe this can help you pinpoint your area... Sightings of T-Mobile 3G/4G/HSPA+ coverage on 1900MHz (PCS/UMTS band II)