I looked for the voucher we had from the taxi, but I can't find them.
How can I explain to you in my not so good English that the prices of the taxi at Puerto Rico are already fixed, so you pay always the same price.
If you get out of the airport there is a kiosk with, like we say kind of traffic agent but different, who controls the taxi's. You tell them where you are heading and they give you a piece of paper with all the prices on it and they point out the amount you have to pay for your destination. It is very easy.