The bottom line, I think, is that credit card, ATM debit and cash are all needed to cover the unpredictabilities in foreign travel. The question for each trip is which is to be the main resource and which is for backup.

1. Credit cards: Necessary for high-ticket business travel and expense accounts, but best considered a backup for most vacations and some business. A card with realistic conversion terms is getting harder and harder to find, and might jack up the cost at any time, as reported in other posts here. Further, shopping around for cards has the downside that you’re playing around with your credit record -- signing up for another card (whether or not you drop the first one) will cost your FICO a few points.

2. ATM debits: Invariably better than CCs these days and could be the best money-saving choice in the Euro zone and other developed countries having plenty of ATMS. But you’ll need to withdraw multiple times because exact cash costs can’t be known in advance. For this reason, it’s crucial to know any conversion and transaction fees at your home bank, and move the account or start a new one at a bank with better terms if needed for frequent travel.

3. Cash: Will get the best deal of all at some destinations. Earlier in this thread I mentioned the quirk that American Express branches in London have cash-exchange terms much better than any electronic access. In the less-developed countries (think much of Latin America and Eastern Europe) cash is king because many places don’t take credit cards, and ATMs may well be sparse and not safe to use at odd hours. Further, many places catering to travellers actually like dollars better than their own currency and will give the same or better than official rates with no fees.

And the safety of carrying cash for the best rates, with plastic as backup? Depends on your comfort level, and not with an amount in the thousands that would be catastrophic to lose. But for a shorter vacation or business trip with land expense under a thousand, I see no concern in carrying enough $100 bills folded over tightly in a thin packet that will stay with you at all times, in some variation of the traditional money belt. (Plus a few twenties in your wallet or purse that a thief in a hurry would take to be your main stash.)

Several of these points are illustrated by a recent 4-day trip to Montego Bay, around the “hip strip” plus some excursions and time downtown, with plastic to cover it all. Credit cards weren’t taken at many places frequented by Jamaicans; I needed five trips to ATMs at conversion and transaction costs of $30 or more. Downtown Mo’bay is a special case, very delightful and colorful during the day, but not comfortable for an obvious tourist target when a different set of characters comes out at night. There appear to be only two ATMs in this good-size town that are outside the closed banks at night. I had to use one amidst onlookers that I didn’t want to meet, and walk fast to the refuge of a nearby Kentucky Fried Chicken. The lesson of this trip? U.S. dollars are accepted everywhere in Jamaica at a fair rate with no fees, and I could have avoided all the above problems simply by tucking a few wrapped-up cash bills in a well-obscured pocket.