Regarding the cell phone use and coverage, you may want to check with your carrier for the following information:
1. International plan coverage for specific ports/islands to see if they cover there, and if so, what are the charges per minute. Then make sure you ask them to set you up on the international plan if you are still interested.
2. check your particular cell phone to see if it has the capability for international plans, if you are interested.
Regarding what to bring, I believe you can look back on some old messages posted at this site to find suggested "packing lists" or search "cruise packing lists" on the web for suggestions from previous cruise travellers.
Hope you have a fantastic first cruise!!