I've been working with this agency to rent a furnished apartment in Recoleta for 2 months: http://www.homes.com.ar/ They appear to be trustworthy, they have certainly been very helpful and informative as I prepare to move down there. We'll move in a week. I've been talking to Victoria, her English is excellent. The only drawbacks to this agency are that the apartments they represent are concentrated in and around Recoleta, I was unable to find a place that I liked in Palermo or Belgrano for 2 months straight. However, this may be because most people who want short-term rentals want to stay in Recoleta.