There are very very few 4br places.
That post is missing
www.bytargentina.com which has the largest selection of apartments but even still, almost everything is 1-2br.
Even if you are searching for stuff at the last minute you would still have a lot of options available for two 2br apartments within a couple blocks of each other. From the apartment page at ByT there's a "See nearby available properties" link that sorts everything for you to make it easy once you find one that you like.
edit: would probably be more accurate to replace "a couple blocks" with "several blocks/a reasonable distance"
Last edited by soah; 10-02-2010 at 12:20 AM.