Originally Posted by GUWonder
Renting a cellphone on arrival at the airport is possible. Just make sure to have a credit card available. There is at least one "desk" right outside customs at EZE where this is possible.
Alternatively, a local SIM card for a GSM phone could work too, but I don't know if that is always worth it, especially if you don't have your own unlocked GSM phone that is compatible with the Argentine used networks.
A third option is the hotels. At least at the Hilton Buenos Aires, a cell phone is generally available for me in the rooms, and forwarding the hotel phone to the cell phone is easily done there.
I checked into getting a SIM card from Telefonica for my unlocked GSM phone, they wanted me to pre-pay for 6 months or more. Some hotels provide phones with free calls in the federal district, before you rent anything check with your hotel.
If you don't have to do business down there you might forgo the cellphone completely, there are 'cabinas' all over Buenos Aires and every other major city where you can use their VOIP service to make very cheap calls. E.g. 5-10 cents per minute international, 2-3 per minute domestic. I have had good luck using Skyp or Vonage on my laptop computer too.