I should add, it may be easiest to book here:
http://www.laslenasski.com/
The owner (Mark Lassiter) is a very nice & honest guy, I've met him a few times.

The price should wind up being the same as booking directly; the hotel/apartment kicks back a percentage to the travel agents.

You can also try mieres.com.ar , though they are more focused on the real estate side. As far as I know Maria Lujan Gimenez Uriburu (who works for Mieres and is a lovely woman) is the only real estate agent handling Las Lenas apartments. Anyway, they are a good bet for a local travel agent.

Remember the A-Factor is hard at work in Las Lenas. Confusion reigns but it always seems to work out.

BTW, when are you going?