Originally Posted by
Eszpresszo
....Discover card would not get him far in any of those countries
Agreed, BUT:
1) Discover owns the Diners Club network, and Discover cards should be accepted by Diners merchants. As a practical matter these are likely to be airlines, intercity rail, chain hotels and high end restaurants.
2) When traveling outside the USA I think it is best to have both MasterCard and VISA from different issuers, because some merchants accept only one of those, and there is always the possibility that a card issuer will shut down a card if international use is not part of the cardholder's history.