I fly to MDE several times a year... when I get up to the ticket counter, they give me a ticket receipt, which I then take over to another desk across the way to the Exemption Desk to get a stamp on my passport. I then head back to the ticket counter and they give me my boarding pass. Somewhat inefficient process, but the Priority AAccess line makes it realively painless. Bottom line, when flying AA to/from Colombia, all taxes ahve already been included in my ticket.