It is legal. But it's REALLY, really expensive! You have to pay wire transfer fees, argentinian taxes, and they give you the value in pesos at official exchange rate.
A much better option is to take a ship to Colonia (Uruguay), and get up to 10.000 dollars from an ATM. (10.000 dollars is the maximum you can pass through customs without problems). You should call to your US bank and let them know that you are going to withdraw that amount of money in order to avoid issues with the ATM.
The total cost is: 2% in ATM fees + fixed cost of ticket (less than 400 pesos in Colonia Express)
