I have also just come back from Argentina and can confirm that it's an easy process to exchange currency. I bought USD in the UK at a bureau de change, and took a mixture of $100, $50 and $20 bills. They need to be new, clean and crisp.

When you are in Buenos Aires, you might be able to exchange your USD into Argentinian pesos directly in your hotel, or they will recommend you go to one of the shops in Florida Street, where all the money changers ('arbolitos') are located. They'll be on the street shouting 'cambio, cambio' ('exchange, exchange').

When I was there last month, the official bank rate for $1 was 165 pesos. If you changed at the unofficial blue dollar (i.e. black market rate) with a money exchanger, you could get between 265-280 pesos for $1. You can barter if you speak Spanish.

​​​​​Cash is king in Argentina, so we ended up changing money every week. It's much cheaper to pay in cash everywhere than using international debit or credit cards. Higher denominated USD bills are generally better for exchanging.

Argentina is absolutely fantastic - loved Buenos Aires but you should try to get down to Ushuaia and Patagonia. Absolutely stunning nature and awe-inspiring scenery.