I convinced my wife to migrate to a GN4 from a 4 year old blackberry. I tested the Nexus 4 with my ATT ST sim with the new settings from XDA. MMS worked fine.
http://forum.xda-developers.com/show....php?t=2461972
but she doesn't tolerate tech anomalies very well. So I got her the $60 prepaid ATT sim with unlimited talk text and 2 gb data hspa+. The $13 extra a month is worth it to have her happy. AIO wireless is $55 a month and does let you BYOD. If you leave for a few weeks and it runs out you have 90 days to renew online. In downtown AUS i get a ping of 120, 5 mbs down and 2 up. Average.