While we're on the subject of currency, you are entitled to have your charges billed in local currency under VISA/MC rules. Hotels will often automatically convert your bill to US dollars "for your convenience" -- which really means using an awful exchange rate to put more money in the hotel's pocket.

You can insist that they charge you in local currency and let VISA/MC do the conversion.

To my knowledge, AMEX doesn't allow its merchants to pull this scam. Whenever I've used AMEX, the bill has been in local currency.