There are at least two ways that tourists in Argentina can be passed counterfeit notes. Both ways are common enough that tourists have to know how to tell a real peso from a fake.
In June I wrote a post about Blue Dollars. There are two peso to dollar rates in Argentina: the official one and the “blue” dollar rate, which is available primarily from money changers on Calle Florida in Buenos Aires. When I wrote the post in June, the rate was 9.07 pesos to the dollar at the official rate and 13.00 pesos to the dollar on the blue market. Today the rate is 9.425 pesos to the dollar at the official rate, and 16 to the dollar at the blue rate.
If you stick to the official rate only, you will be paying more for everything; but you will probably not wind up with fake pesos—if you stick to major bank ATMs. (Money changers and dicey private ATMs are a different story.) First of all, to deal on the blue market, you need crisp, fresh Benjamins, that is to say, one hundred dollar notes. When dealing with a money changer, you have to indicate you want money at the blue rate, and you have to be willing to closely examine the bills you get in return. You can look at San Telmo Loft’s posting on “Fake Money in Argentina” for starter. And be sure to take their quiz.
Another common way of getting stuck with counterfeit notes is to use legitimate big bills and having the following happen: Let’s say you give a taxi driver a real 100 peso note. He turns around, gives it back to you, saying it’s a fake. In the meantime, he’s pulled a switch on you. Before handing over a big bill, be sure to memorize the last three digits of the serial number. That way you can accuse the driver of having passed a fake to you. You might not want to be standing where he can run you down at that point.
Fortunately, it’s easy to tell fake from real notes; but note that a lot of fake pesos are in circulation. If you get stuck holding them, there is no real recourse.