Based on the map on Verizon's site, they don't have CDMA coverage in the Bahamas, so no voice calls:
Calling From Bahamas
The same map shows 3G coverage. Of course you will have to pay the rates shown on this page:
Data From Bahamas
If you don't call Verizon to set up an Int'l plan and just use the Pay Per Use of $.02 per kb it adds up fast. That's $20 per Mb.
Example: I average 2Gb per month of data. Divide by 4.5 for a week usage (1 week vacation) equals 444Mb or $8,880 for one week of data in the Bahamas on the Pay per Use plan.
Turn off data: Settings / Data Manager / Data Delivery / uncheck all 3: Background Data, Data Roaming, Data Enabled
or just put the phone in Airplane mode for the entire trip.
If your hotel or the local coffee shop has WiFi, you can use the Droid X WiFi all you want. That doesn't use Verizon's data.