Some info on AT&T:
When there with my son a few times, noted that 3G service is almost non-existent - with Nokia and iPhone 3Gs. EDGE data access is fine out in the open, but almost nothing inside many of the buildings if away from windows. Also, no public WiFi access for smartphones or laptops; not even in the Library. Not sure if there might be hidden/secure Wi-Fi. Library did have Ethernet jacks at the study tables.
Call and Text capability was just OK. I don't recall missing any texts or calls while around the various places, but call quality was much better while outside or near windows when inside.