It is getting easier (than it used to be) to cross border between Villa O'Higgins and El Chalten (via Lago del Desierto).
It is a very beautiful alternative to the shaky bus on Ruta 40 from Perito Moreno (city) to El Chalten.

All information on :
http://www.villaohiggins.com/crossing/border1.htm

I've updated the El Chalten page accordingly.