We use option #2 daily at work, except you don't have to enter a username/password. Your device is already programmed with these. As Abom states, it will automaticly use the fastest available speed, and automatically drop down to
1xRTT if it has to. One thing to note is if your in a "fringe" area, you might see
EVDO but not be able to connect due to your distance to the nearest ariel. So you should try to force your device to
1xRTT and see if that works.
As for cost, this depends on your data plan on your phone. So I'd call customer service and see what plans and charges are available.