Go where the A44 crosses the A329 (location on map), and get on the A329 towards the A92. This is the motorway between Sevilla and Granada.
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 motorway anyway): Where "Carretera de Jaen" (also called "Av de Juan Pablo II"?) and the A44 meet, you find a big roundabout below the motorway. 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.
Get any of the entrances next to the A44 and use the direction of Lorca/ Guadix (A92 and later A91). Best thing would be to wait for someone who actually is going into that direction since the A44 crosses the A92 after 5-10 minutes.
Go with the bus 122(Timetables http://terapiaquantica.es/linea_autobuses.pdf) from Caleta or Estacion de Autobuses to the first stop in Albolote, walk there about 5 mins towards the A92, which is the Motorway between Sevilla and Murcia, take a view on the right and choose the petrol station that leads you the direction you want to go. It is a really good spot, takes between 2 minutes and 8 hours. Direction Sevilla there is one more of the good gas stations, right after Lorca. The other way you have one directly when you come close to guadix, might be like exit 296.
Works not so good in direction Malaga. Direction Malaga is completely Spanish typical. That means 'Get lucky or you're screwed.'. We were 3 people and one driver could only take 2 of us so I just stayed there for the next 8 hours and nothing happened. Went back to town, took a 5 euro bus south to Motril and camped near the city as its pretty small.
Direction Málaga via Santa Fé
We walked all the way from Granada to the first gas station in Santa Fé, which is definitely not recommandable (but doable in a way). However, talk to people there and hope that the gas station guy doesn't mind. He did when we tried, but got lucky in time. It took us one car to get all the way to Málaga! (September 2010)
Granada (map) has a national motorway called A44 just around the city. There are many exits on this motorway. When you are on the A44, wait for exits with direction city center. The driver can easily get off and on the A44, in either direction.
If you talk to nice people in the Albayzin, they may be able to help direct you to some nice camping spots near the caves in the hills of Sacromonte. However, prepare for a bit of a hike with heavy gear. Anyway, you can find spots to camp outside the city on your own: from Albayzin it's not far to the woods above the city.
There is a weekly couchsurfing meeting in Granada (Winter 2009/2010 it was each Wednesday) in Granada - Time and place in Granada's couchsurfing group. You might have some luck to find a couch, just going to that meeting and get to know hosts for a night.
Other Useful Info
Free entrance to al Hambra : Al Hambra is the most impressive and visited Granada monument, very beautiful but very expensive though, about 15E with no reduction (maybe 10 for students), Free entrance are options are 2: 1) a bit more "legal" is the free resident ticket. Every first sunday of the month or every sunday (check with locals) the entrance is free for every citizen living in Granada. You can just ask your Couchsurfer, some friend or anyone also have a rent contract to falsify it and put on it also your name. At the office they won't check it, and they will issue a free ticket for you. The problem is that tickets are very few and normally are already finished the monday before. so you will probably be obliged to follow option 2 2) is the classical free entrance to any open monument (not a church, building, cave or anything else with only one entrance) and consist in find a spot to enter the net and later behave as a normal tourist. In AlHambra is quiet complicate cause is full of guards and checker at every entrance (they control your ticket at the entrance of any building). Just take a map of the area at the main office, it's not that detailed but it's free. You will have to enter from the hill of the "Generalife" palace, is the farest one, you can join it also from albaicin quarter. Climb up the hill a little, you wll find lots of paths. At a certain point you will see a net, holes in lots of points, just pass under it but it's not finished. You will be inside Generalife area but normally tourists can't go there so you will have to enter tourists path without make you notice and it's not very easy. Just check your map and wait for the right moment. Your luck will help you. Once in, enjou the gardens, follow all paths in the wrong sense, but once in the area never enter any building from the entrance, they will ask u for the ticket , now you are just as the other tourists don't worry. Enter Nazaries palaces (the most amazing area, they have scheduled time and neither paying tourists can enter them back twice) will be almost impossible but you may try your luck as well.
- I entered AlHambra for free (Jan 2012) in the only rainy day of andalusia but enjoyed as well. I was about to enter also Nazaries palaces cause there were open works in progress but they caught me. I just explained I wanted to stay more, they smiled me, said was not possible and let me go. I could visit the rest of the complex though without the ticket..Fedecicco