Hire an organizer of "Ferias Americanas" to run a weekend house sale for you. You will find their ads in the classified ads of La Nacion. Call Roxana; she has been in business for many years and speaks English.
Advertise in La Nacion and/or Buenos Aires Herald and try to sell the furniture taking calls or running the sale yourself.
If you are in a hurry, the organizers know what to charge in order to sell it in a day. Some of them have websites and will put up photos.
Find a second-hand store that buys furniture or donate it to the Salvation Army who will pick it up in a day or two.