We always find an A TM at the arrival airport to get a small amount of local currency. Then we just use credit cards or if you are in the first port of many that will use Euros get some of those at the port terminal ATM. You will find that you really don’t use much in actual currency unless you are in a small market to buy souvenirs or you just want to buy water or a drink and of course for tips if you are take a tour, although the tour guides will be happy to take US dollars too. We always take $100 in 1s, 5s and 10s to use for tips. And usually about $300 or so in 20s to add to the tip envelopes for servers and our cabin steward at the end of the cruise, in addition to the tips that go on our room charge, we add something extra in cash depending on the length of the cruise and the service, I’ve added as much as 100 for the steward and usually around 50 for a good server. And at the end of the cruise I always leave extra for my barista in the Cove and a favorite bartender.
We always seem to end up with extra currency when we get home. I keep it all in an envelope...pesos, euros, pounds, etc. and try to remember to take it on our next trip.
If this is your first time out of the country, try to conform to local customs so you don’t come off as ugly Americans. Cover up in churches, don’t be too loud, say thank you a lot, smile and be nice. And if you have the chance to talk to locals, do it. We have been all over the world and find that most people from other countries love to,talk to Americans. I don’t know what your political Bent, but Be prepared for anti Trump sentiment which seems to be rampant. If you disagree, just nod politely and change the subject. If you agree, then have at it! Political discussions with non Americans can be so much fun. And if you are traveling the British Isles, Brits and Scots love to rant about Brexit, either for or against. Another fun discussion.