Unless you’re heading someplace particularly rural, you’ll should be able to find an A.T.M. with ease. Besides, depending on the country, stores probably prefer credit cards anyway.
As far as credit cards go, outside the United States, American Express and Discover cards aren’t nearly as widely accepted. Visa and Mastercard are far safer bets. Ideally, bring a card that doesn’t charge foreign transaction fees. Wirecutter, The New York Times company that reviews products, has a number of card recommendations that don’t charge those fees and offer other perks. If you’re not sure about your current card, call the company and ask — and always let them know before you travel so they won’t flag your foreign activity as fraud and freeze your account.
If you pay by card, some places will let you choose to pay in local or your home currency. Paying in your home currency will likely cost more as you’ll get a poor conversion rate and a transaction fee for the “privilege.” Unless you know your card charges big foreign fees, paying in local currency is cheaper.
Mobile payments, like Apple Pay and Google Pay, or apps like Venmo and Square where you’re able to use your phone to buy things, are growing in popularity at home and abroad. However, these aren’t widespread enough to rely on as a main form of payment. Their availability will depend not just on the country you’re visiting, but the specific shop you’re in.
Most of the clothes you’re thinking of bringing
You don’t need a different outfit for every day of your trip. In fact, unless you have to bring something bulky that’s specific to your destination — a winter parka to see the Northern Lights, custom fins to dive the Great Barrier Reef — you should be able to do any length of trip with carry-on luggage and a day pack/big purse. My longest trip so far was just under five months, and I brought a 40 liter (roughly carry-on sized) backpack, and a 15 liter day pack for my camera and other electronic gear.
If you’re gone for more than a week, just budget two hours sometime during your trip to do laundry. Pretty much every hotel, hostel, and Airbnb will have laundry facilities in the building or nearby. (But avoid the exorbitant cost of having the hotel do your laundry for you.) Worst case, you can hand-wash in a sink. I’ve only had to do that few times.
What to pack? I usually bring six shirts, underwear, and pairs of socks, plus jeans and shorts. (You might consider adding a pair of khakis or dress pants for an evening out.) I’ve met people who bring less, but enough for one week seems pretty common for frequent travelers I’ve met.