If I recall correctly when they charge the bill in say, US dollars and you are in the Euro zone there are fees that both the credit card and the merchant add onto the bill for "conversion". This adds several percent to the bill and the exchange rate conversion is not the best. That is why it is recommended that you request the charge in the local currency.

You should mention it when you check in but should they "accidentally" do it in your currency you have every right to ask them to void that and re-calculate it in the local currency.

Nancy in VA