If it is your first time in Buenos Aires let me advise :

Best areas to stay: 

Recoleta, Palermo, Downtown. If you like french glamour and be close to touristic things is Recoleta. If you like nightlife and trendy ares is Palermo. If you don´t have enough budget and want to be close to touristic areas is Downtown.

Economy: In 2014. We have 2 markets where you can change your money. The atm  or the official market at the bank (pesos 8) or the hidden caves where you change for dolar blue or paralel market or black  market (fluctuation but around 1o to 12)

Security: The city is safe but don´t wear gold, expensive watch, take care with your camara and cells and iphones or tablets. No violence just they will look for your distraction and you will never notice.

Walk: The city is like New York , a walking city. Big as Madrid, Paris, ,Rome, London.

People are friendly. Taxis as in every big city. Food is delicious for malbec wine, steak, dulce de leche, alfajor, empanada.

Time: Things start at 9 to 10 , lunch at 1pm, tea time at 5 with mate, coffee or tea, dinner around 9pm and later during weekends.

Tango. Is a must! Go to a Tango Show and a Local Dance Hall.