I spent the last two weeks of June 2013 in Buenos Aires.
Shop keepers and street vendors often accept US dollars and give a better conversion rate than banks and credit card companies.
Banks will generally use the official exchange rate, which in June 2013 was approximately 5.4 Argentine pesos for one US dollar. Credit card companies will also use a rate close to the official rate but most also charge a fee of 2.5% to 3%.
Shop keepers and street vendor rates were between 7 and 8 pesos to the US dollar with no fees.
To get the US dollar rate from retail stores, agree on the price in pesos, then ask how much would this be in US dollars, in cash. The shop keeper will often take out a calculator and show you the peso price, divided by the exchange rate he or she is giving. The rate in June of 2013 was 7 or 8 pesos to the dollar and gives a significant saving over the official rate of 5.4 that you would get with a credit card or at a bank.
Another way to get a better rate is to change the money on the street. Florida is a major shopping street in Buenos Aires. On every block, there were several people standing on the street saying the Spanish word “Cambio”, which is an offer to exchange currencies. Rates varied from 7.8 to 8 pesos to the dollar.
When getting a higher return for your money, you are, as always, taking additional risk. Cash can be lost or stolen. You can mitigate this risk by leaving most of your cask in the safe in your hotel. If changing dollars on the street, it is probably better not to change too much at any one time and be sure to see the pesos you will receive before handing over your cash.
If you take more than $10,000, currency or other monetary instruments, out of the US, remember to file form FinCEN Form 105 (www.fincen.gov/forms/files/fin105_cmir.pdf) with U.S. Customs and Border Protection. It is legal to take the cash; you just have to file the form.