From what I recall, US Cellular is CDMA. The 9630 is both CDMA and GSM. You need to unlock the GSM portion if it isn't already to use on a GSM carrier. Keep in mind that you will not get 3G speeds, only EDGE using GSM.
Thanks for the feedback, AK & Dub. After talking with the user about why he needs access on vacation and the pluses & minuses, he's decided to go without. Frankly, if I was headed to the Bahamas for vacation, I don't think I'd want to hear my phone ring or feel it buzz...