Foreign currency purchase restrictions in Argentina
Since the introduction of a new currency restriction policy, it is literally impossible to purchase foreign currency especially dollars in Argentina.
Individuals can only purchase up to $10000 per month and there should be extraordinary reasons behind the purchase. Businesses need to get a permit from the central bank of Argentina in order to purchase foreign currency.
My advice: Exchange only the amount of money you'll need to use while in Argentina to Argentinian pesos especially if you're not from a South American country since exchanging back Argentina pesos to euros for instance in a European country is likely to get you a really bad exchange rate.