If you fly on your international trip to Argentina with Aerolíneas you sometimes get discounts on domestic flights. Sometimes you even get free flights with your international ticket but keep in mind that you pay it with your international ticket.
An amazing train ride is the Tren a las nubes (Train to the Clouds) in the northwestern province of Salta, but some people may get altitude sickness.
Traffic regulations in Argentina are generally the same as in the US or Europe, but the local often ignore the regulations. Maximum speed: 60km/h in the city, 40km/h on side roads and 100km/h to 130km/h on roads outside the city as well as on highways. However speed limits and lane markings are universally ignored, and running red lights is common. Make sure you are thoroughly confident in your driving skills before attempting to drive in Argentina.