Actually you must
use a credit card...well perhaps you can pay your bill in cash at the end, I'm not sure, but when you board the boat you 'open an account' with a credit card. All expenses (gambling, spa, specialty shops) including the 65 euros per person (gratuities for cabin steward and dining staff) are charged to this account. You get a final statement in your room the night before you leave.
I'm not sure if they have a foreign exchange office on board but there are plenty in any of the ports. You won't need a dime while on board.
I can't recommend any excursions as we didn't do any, however I can say, if you plan to go to the Virgin Gourdas whilst in Tortola, and if you plan to do it yourself (i.e. not with the excursion) leave as early as possible (like 8am) to allow yourself time to get the ferry back since the cruise leaves at 3pm that day.
There is an information kiosk at the end of the dock in Tortola...they will give you all the info.
It is roughly half the price to 'do it yourself' as opposed to doing the excursion.
I found the excursion prices a bit high but they do make sure everything is taken care of (transportation, english speaking guides, etc) but make sure you mention to the excursion woman if you have any special requests. She is super nice...but then, everyone is on the boat!
As I said in my original post, I've never been on a cruise before but I would rate the boat and facilities at about 4.5 and the food would be a 6 (on a scale of 1 to 5). If you REALLY want to see the shows, know they are in Spanish. That didn't bother us so don't let it bother you!