Got the AT&T MicroSIM, popped it in and it works fine
Had to discuss with the people at the AT&T store to get data but at the and they activated the data plan for me
They said the One X doesn't support data on the GoPhone PrePaid plans...
Really liking AT&T, it's HSPA+ coverage and the HSPA+ speeds. Much faster than my operator in Germany (it's the 2nd worst out of the 4 operators we have, gotta change soon).
Here in San Francisco I got 6.2Mbit/s down at 23:11 yesterday with the GoPhone 1GB Data Plan
Couldn't test in Vegas, these guys really didn't want to activate data and the Taxi waited outside so no time for long discussions, got data activated here in SF
Strange thing is that the Speedtest app doesn't work with the MediaNet APN.
Using the "phone" APN anyway to get full HSPA+ speeds and with that it works fine.
Another strange thing here is that I had to enter " phone" (with space) instead of "phone" for the APN to get an internet connection.
But now it works fine and I'm happy
Thanks for the help guys