Wrong forum for this but what the heck, I'll provide some info:
Credit cards are great, even in the US, as long as you pay off your balance in full every month. That way you avoid their usurious interest charges. I've used credit cards for the majority of my spending for over 30 years and I've never paid one penny in interest. Also many cards w/o any annual fee offer cash back reward programs, or programs that reward you with miles that can be used for free air fare. So you can make money by using the right credit cards wisely. Also, if you ever want to rent a car, I think you must have a credit card. I really can't imagine not ever having had a credit card unless you are very young, which perhaps you are.
Almost all credit cards charge hefty foreign transaction fees for charges made outside of the U.S. (or one's home country). However, there are a few cards that do not. Capital One's credit cards are the one company I am currently aware of that still does not charge any foreign transaction fees, so I always use their card when traveling abroad. They also offer a 1% cash back reward on all transactions through their rewards program.
In addition to the foreign transaction fee (that Cap One doesn't charge), most Visa/MC credit cards also add a small fee to the exchange rate for currency conversion when one buys things in a foreign currency. The amount they charge for currency conversion can vary depending on the card issuer, however, Visa/MC themselves only charge 1% unless something has changed since the last time I researched this. Cap One doesn't charge this fee either iirc. Also generally Visa/MC credit cards provide excellent exchange rates (if you can avoid the above mentioned fees). Usually they are better than what you could get at a bank in a foreign country.
However, cash advance fees that credit cards charge are expensive, so one doesn't want to use a credit card to get hard cash in a foreign country unless absolutely necessary.
The best strategy, imo, is to use a Cap One card for all purchases and payments that one can overseas. And you still can even earn 1% cash back rewards on those transactions via their cash back rewards program and you get visa/mc's excellent exchange rates on those purchases or charges.
Then also get an account and ATM card from a bank that doesn't charge ATM fees in foreign countries (there are a few out there, e.g., some credit unions and USAA Federal Bank), and use your fee free ATM card to get cash from ATMs in foreign countries for expenses that can't be paid with a credit card.
That's basically the way I do it and it is based on having done a lot of research to figure out ways to save money.
Peter - My 's:
Caly~3.5 (VG-10 & S. Blue); Para2~(20CP~M390~S30v); Military~(M390~S30v); Endura & Delica~4~FFG; Native~(S30v); Caly~Jr.~(ZDP); Manix~2~(M4); Ladybug~3~(VG-10. SE); Mules~(M390).