I travel internationally for work, and AT&T passport is for data and calls. If you plan to use cellular data and not just wifi, you will want an international plan. If you are okay only using wifi, then no need for an international plan. International roaming cellular data is terribly expensive - even with a plan, when I go over, my bills can be more than $500 per month.

There are some other options in the BVI like getting an unlocked phone and buying a local SIM card. Really all just depends on how in touch you need to be with home.