For us, we're thinking that we want to have enough cash for the first few days in Barcelona and will get some cash at the ATM. We know once we are onboard, we can exchange US cash, so we are figuring out if we want to take US Cash (or traveler's checks, etc.) or just use the ATM onboard and then exchange with
DCL. Here's something good to know - if you find yourself running low on cash, DCL will cash a personal check up to $100 US - we've done that before instead of having to get cash from an ATM.
We don't want to arrive without at least some US cash and some Euro - here's why - we went with NO Canadian money when we went to Vancouver - just planned to get some cash from the ATM - and we took limited US Cash as we knew we could always get some at the various ports in Alaska. Well it turned out that our bank's debit card would not work in Canada - not at an ATM even with the MasterCard logo nor when processed as a credit card. Thankfully we had a credit card with us that we could use, and there were several places that accepted US cash but gave change back in Canadian - so we were able to manage but ended up boarding the Wonder without the cash we had wanted for things like room service tips, etc. We did call our bank while in Vancouver and found out that it's some weird thing with Canada, but considering we had called to notify them of our plans and specifically asked about using our debit card out of the country (and stated it was in Canada), it seems they should've told us it wouldn't work. A few weeks after we got home (and after my discussion with a supervisor about my disappointment and inconvenience), I noticed that they put up signs at the teller windows that if you're traveling out of the country, please ask if your debit card will work!
We've done DCL transportation on overseas cruises and found that they don't get you to the port in the first wave - but a little bit later in the boarding process. So pretty much they have it so you can get right on board when you get to the port, or very soon afterwards. If you have paid for DCL transfers, I don't see why you can't have them take your bags and you go site-seeing and get yourself to the port in time - but remember to leave yourself plenty of time to get there! It seems that when we've done DCL transfers, when we do our check-in at the hotel, we get to sign up for the transportation time over to the port - first come, first signed up - but never really early. I know we've had leisurely mornings at the hotel before heading over to the ship.
We will have 1 1/2 days in BCN before boarding day, and another day when we return. Plus we've been there once before so we've done some of our site-seeing already. We learned the first time that if you don't plan properly, you miss seeing the departure port - and that's a shame. If you come in too late, you're too jet-lagged and then get right onboard the ship and totally miss an amazing city.