2 hours leaving on a friday night for the north or coming back to Capital on a sunday late afternoon : search for a house 30/40 miles away, no more (huge traffic jams).
You have Pilar (I live nearby, it's very pleasant), Campana (which has very nice natural parks nearby).
A bit further you have San Antonio de Areco, Capilla del Senor.
There are good opportunities at times to buy land but if you won't live there during the week, better buy in a barrio cerrado, otherwise you can be assured to run into problems even during the first year.