NORTH:
A good place to start is Granada's service station ("via de servicio") in the north of the city (that's where most of the people heading north enter the highway motorway anyway):Where "Carretera de Jaen" (also called "Av de Juan Pablo II"?) and the A44 meet, you find a big roundabout below the highwaymotorway. Take the exit "via de servicio" (or if that exit doesn't exist, then "poligono indistrial" - sorry, not sure!) There's a gas station where you can find a ride.
Have in mind that most of the drivers there will go to Jaen.