The currency on all RCI ships is US$ irrespective of where they are sailing.
We have just got back from a first time cruise on the navigator of the seas.we gave them our bank card(visa card).they take all your details and then give you your card back.They then give you a seapass card, which you use for anything you purchase on the ship.There is no cash used on the ship at all.This card is also your key to your cabin.. we had a wonderful time and the crew couldn't do enough for you..it was so relaxin.
I Cruise regular on US ships. Your Credit Card will be swiped prior to boarding & I normally allow it to be charged to my card. I always find rate charged by CC/Bank to be very favorable. You cannot pay in Sterling, just let your credit card do the work & enjoy it.
There is another alternative and that is to purchase US dollar traveller cheques now to take advantage of the weak dollar.
Then when you get on board you can set up your Sea Pass account with your travellers Cheques. If you have any money left in the account you will receive it in cash the night before you disembark.
This process is very easy and saves on currency conversion charges when using a credit card.
On our last cruise a few weeks ago a number of people were using this method of setting up the Sea Pass accoun.
The currency was not US dollars when we sailed on Legend of the Seas from Southampton in May 2006.