ST always shows Home as the network even though it's AT&T. The Atrix is an AT&T phone so you should get at least 3G. Make sure your APN settings are correct and in the network settings it shows HSPA preferred.
If you ported the number over sometimes it takes a day or two for all the configuration changes in the system to take effect. Sometimes the port doesn't finish up like it should and you have to call them to check/refresh the data.