I was digging through our international coinage over the weekend and came up with 9,75 Euro that we'll take with us to have some coins to start with. We'll exchange for some Euros before we leave so we won't have to immediately find an ATM, and because we're doing a Rome in Limo tour that requires Euros in cash for payment, we'll go ahead and get that out ahead of time, too, so we'll be absolutely certain we have that.
You can exchange US for Euros on the ship as well over at the shore excursions desk side. And they'll exchange back for you at the end of the cruise as well. They may have some restrictions on what they'll take back (like certain denominations in bills, not coins, etc.) so just know that has been an option in the past.
We have old Nokia non-smart phones so we aren't going to have cell-phone service while we're gone, but we do have iPod Touch and iPad that we'll be traveling with. The iPod Touch will always go off with me so when we do find a hotspot, we'll check in with home. I have used the ship's wifi before but what I found worked best is to just buy a plan and then download the email, disconnect, reply to whatever needed replies or write whatever I wanted to send, and then connect again to upload it. I had a blog I did, too, that I could post by email to - I will probably do that again this time. Just no pictures because of how much it takes to post them. I have found that the ship's wifi worked good enough if you used it when most people were still off the ship or very early morning or late at night.
Some research will probably point us to free wifi hotspots in the ports.