Haven't experienced this directly first hand, and I am always given the little machine to choose whether I would like to my card to be authorized in USD or EUR.

Hilton Barcelona, Hilton Madrid Airport, and Hilton Brussels City did not do that--just charged me in EUR. DoubleTree Westminster (in London) passed me the card terminal to choose.

I did have an experience at a small villa property in Marbella where the innkeeper pressed USD for me instead of letting me choose. Granted it wasn't a Hilton property, though I would like the $20 back.

Staying at Conrad Dublin, Conrad London St. James, Hilton Prague, and DoubleTree Victoria in the next few months and I doubt we'll have problems, but we'll see/