Banco de la nacion...open 24 hours...is the best place in Buenos Aires to exchange money. It is far better than the kioskos or exchange houses at the airpórt, and slightly better than other exchange houses downtown. As you exit customs, it is located to your right. Also, there is a window inside the customs area.....The ATM works with both Cirrus and Plus system.
Taxi...the fare for taxi has gone up to 51 pesos, including fares. The blue and white booth inside the lobby or the yellow and black booth outside are both safe and reliable. A remis will cost only slightly more, 55-60 pesos depending on the company.