The Argentine currency is the peso, and it has the same symbol ($) as the dollar (don't be confused - prices expressed using the $ symbol are in Argentine pesos unless stated otherwise. US dollars are referred to using the symbol: U$S.
It is easy to exchange money in Buenos Aires at casas de cambio (bureaux de change/currency exchanges) and at most banks. These are by far the safest places to change money and you will need to provide identification in order to do so.
Illegal money changers operating in the street, particularly in areas such as Calle Florida, may claim to offer a slightly better rate for dollars and euros than banks and casas de cambio, but for safety it is advised to change money at regulated institutions. For the same reason, we do not advise changing large amounts of money at one time.
Local currency can also be withdrawn from ATMs, and larger shops and restaurants usually accept payment by credit or debit card.
Foreign tourists are eligible to reclaim tax (VAT) on all purchases of domestically-manufactured goods with a value over ARS $70. The Global Blue website has useful information on the tax reclaim process here: http://www.globalblue.com/customer-services/tax-free-shopping-in-argentina/. AFIP, the Argentine tax authority, also has information in Spanish here: www.afip.gob.ar/turismo/.
Some businesses (restaurants, hotels, shops) will accept dollars in cash. It is always worth asking.
Many shops often run low on small change - both coins and small denomination bank notes. They will be very happy with you if you can pay with the exact change.
If you have a large amount, you can exchange you US dollars at an official casa de cambio or in a bank (it may also be possible to exchange them for euros, or Brazilian reales, but other currencies are not regularly stocked). You may be asked to provide receipt from your original sale of dollars in order for you to buy back dollars. If you have less than ARS $1,000 leftover, it’s probably best to use it for transport to the airport or for buying souvenirs.