The currency in legal process is the Argentine peso. The change varies a lot but a euro equivalent to 5 pesos and a dollar American at 4 pesos. Keep in mind that we are talking about a very fluctuating economy, so these changes are only approximate.
The banknotes in circulation are 100, 50, 20, 10, 5 and 2 pesos, and the coins of 1 peso, 50, 25, 10 and 5 cents (there are 1 cent coins, but they are hardly used anymore).
Banking hours are Monday through Friday from 10:00 a.m. until 3:00 p.m. There are numerous authorized exchange houses, these usually open in the afternoon and in many cases on Saturday mornings.
The most widespread and accepted credit cards are: American Express, Master Card, VISA and Money. They accept them in all shops, although in many the price is lower if you pay in cash. You have numerous ATMs available to withdraw cash. And honestly, it is not a bad option. The commissions charged by Spanish banks for extracting money abroad are not so high and in many cases the exchange rate is better. If you are going to opt for this option, I remind you that you are charged for each time you take out money, which is why it is advisable to get a higher amount than to withdraw several small ones.