i would only go to mendoza, as you have limited time and it is the largest. i would prearrange a meeting with:
"The two largest companies are Bodegas Esmeralda (which owns the widely exported brand Bodegas Catena Zapata) and Peņaflor (which owns another widely exported brand Bodegas Trapiche). Between the two of them, these companies are responsible for nearly 40% of all the wine made in Argentina."

unless they are already in china, and have exclusive arrangements with an importer.

this is a list of over 100(i did not count) mendoza producers:

http://andeswinezone.diariodelvino.com/maps/mendoza.htm

there are more producers here than in chianti or california, it seems