Comodoro Rivadavia is a city in southern Chubut, Argentina.
North towards Trelew
You can take a local bus toward Astral. It only passes once every two hours and costs about 7 pesos as of March 2015. There's a police checkpoint in front of a gas station leaving town, which is probably your best bet. You could also try staying on the bus until it turns off the main road (Ruta 3), and then you walk along the Ruta 3 for about 500 m, and there's a little rest stop where you might have some luck.