Salamanca

South towards Cáceres

Option 1: Has more traffic than option 2. Take the bus Linea 11, direction "Buenos Aires", get out at the last stop. This bus will take you to the western most extremities of the city from which you will be able to hitch a ride along the A-62 west and of course the A-66 south. The best spot to start looking for a ride south would be the one shown on the link below. You have to walk from where the bus drops you towards the highway, jump a fence to reach it and then cross it to the other side, but then as you can see at the left of the map in the link you will find a nice flat land field where cars can safely stop to pick you up.

LINK [1]