Take the 27 de Febrero Avenue and follow it all the way west. You will eventually come to a traffic light at the crossing of Isabel Aguiar highway, beyond the Plaza de la Bandera, a large rotunda with government buildings around it. Continue north. Do not go under the tunnel. Continue north and the highway will do a turn to the west taking you on to the 6 de Noviembre San Cristobal Highway.
Always recommend people to ask and ask. Your key words are: Avenida 27 de Febrero, Herrera, Isabel Aguiar, Autopista 6 de Noviembre a San Cristobal.