I don't have the answer because I have never sailed with Costa but I would like to make this point: If you have booked then I would suggest that you read the back pages of the brochure, visit their web-site and look through the FAQs and read the Berlitz Guide on this site. You will find loads of things, other than those mentioned, that will be pertinent to your cruise. I am not getting at you for asking and I'm sure you will get the answers to your question but I feel that it will enhance your cruise to do what I suggest .. regards ..... Nei.
The currency used is the Euro and the dress is quite casual we have found on our two cruises with Costa. i.e. a blazer and trousers is quite acceptable for formal nights as opposed to a dinner jacket...we even saw jeans and tshirt with trainers at one of the formal nights in the restaurant and nothing was said!!!!