Martínez is a city in San Isidro Partido, Buenos Aires Province. It is part of Greater Buenos Aires, and effectively a suburb of Buenos Aires. It is …Martínez is a city in San Isidro Partido, Buenos Aires Province. It is part of Greater Buenos Aires, and effectively a suburb of Buenos Aires. It is served by a commuter train service, the Tren de la Costa tourist railway line, and many buses.