Bariloche (officially San Carlos de Bariloche) is a city in Rio Negro, Argentina.
North towards San Martin de los Andes
You can take the 71 bus for 12 pesos (~1 USD, as of December 2014) to Dina Huapi (about 15km outside of Bariloche). Stay on the bus until it turns off the main road. You can ask the driver, but it's pretty obvious, and there's a stop as soon as it turns. Depending on which 71 you're on, you'll either have to walk about 100m or 1km along the road to a police checkpoint along a curve where traffic slows considerably and people can pick you up. Another way is a traffic light right next to the bus terminal within walking distance of the town center (3 kmg). You can also always start hitching on the main road inside the city which seems to have a lot of tradition. Chances are good you will be picked up before the bus even arrives.
South towards El Bolson/El Calafate
The way out of Bariloche towards El Bolsón is through the barrio 2 de abril, which is rather universally described as a dangerous place and lots of people recommend avoiding it for your own safety and because drivers are also less likely to stop there, due to its reputation. Hostel owners speak of a few cases per year where people get a ride but are then immediately forced to get out of the car and eave all their stuff with a gun held to their face.