You're not going to get any success at all while you're in the US.
Also, as I already posted earlier in this thread, the phone seems to disallow any form of roaming. My Irish SIM is working OK here in Ireland, but it disconnects when I go out of the home network area - it doesn't connect to any roaming networks. (It roams fine in my TouchPro2.) It likewise would not connect while I was in the US (but in my TP2 it connected to AT&T roaming just fine).
T-Mobile G1 / radio 220.127.116.11 / SPL 1.33.0013d / Recovery RA-dream-1.7.0 / FroyoByLazlo-4
T-Mobile TP2 (RHOD210) / radio 18.104.22.168 / WM6.5 / XDAndroid FRX06+Fixes
Verizon Droid4 / 6.16.217.XT894