Merida is a city in Spain.
Walk or bus!
South/West towards Lisbon, Portugal
Merida is a great stop to get to Portugal and Lisbon. It's along the motorway A5, leading to Portugal. There is a bigger stop, with a petrol station at both sides of the road, northwest of the city, where the Ex-209 crosses the motorway. You can get a ride to Lisbon or Sevilla from there. Try getting to Badajoz (ca. 30km) which is on the border and where you're sure to get a ride to Lisbon.
North/East towards Madrid
The Repsol gas station near the exit is good. You can find a ride to the next Cespa gas station a little upper. Not a lot of cars are passing by but those who do all go in the direction of Madrid. You can wait at the exit of the station so you can catch all the cars.
Walk or bus!
Accommodation and Sleep
Eat in the restaurant on the west side of the motorway, tortilla (ask them to warm it up) and coffee are cheap and good!! Sleep on the west side, there is a restaurant behind the petrol station, that closes for the night. It has a terrace; no-one disturbs you, you're covered from the wind on one side.
The albergue (hostel) Molino de Pancaliente, which is part of the Camino de Santagio network, is a few minutes walk north of the Puente Lusitania, on the east side. It costs 6 euros/night. You can find it by walking north from the puentes Romano y Lusitania for about 10 minutes. 
Other Useful Info
This is Extremadura! Hot during the day, freezing at night (hoodie, long trousers, hat even in July).