I'm based in the US but will soon be buying a DONE3 originating in MAD. What is my best option for ticketing? Call AA in DUB? AA in Spain? The AA RTW desk was emphatic that I'd be charged the US-originating price if I just purchased from an ordinary US RTW rep.

Is there any way to pay in USD so that I avoid my credit card's ~3% currency conversion surcharge?

I'll be in a bit of a rush when I get to MAD, so I'd prefer not to ticket in person at the airport.