Cheap Option: Subway (2.50 pesos)

Once you have arrived at the bus station, enter the terminal and head right. Keep walking until you see a ramp, walk down the ramp and you’ll be outside. Turn right and walk approximately 4 minutes until you see a little flea market outside a huge old building which is the train station. In front of it, you will have the subway station. Purchase a ticket for 2.50 pesos and board the “C” Line (also known as blue line). The subway from this stop only go one direction, so either wagon will do

In the subway, travel 6 stations (Saint Martin, Lavalle, Diagonal Norte, Avenida de Mayo, Mariano Moreno, Independencia.) You need to get off at Independencia, walk to the end of a long corridor, and exit via a staircase.  Once outside, you will find a Shell service station on the corner of Estados Unidos and Lima. Continue walking down Estados Unidos until you reach Salta (only one block), turn left, and look for us at 990 Salta.

It is between the Estados Unidos street and Carlos Calvo.
In short, walk to the subway station, take line "C", get off at Independencia, look for Salta street, and walk two blocks from until you arrive at PAX.