In reply to Davy Virdee: for a start there is the ruta integrale de los tres mils, a multi day ridge walk and scramble covering all the 3000m peaks in the SN, there are parts up to Vdiff, but a lot is just walking or easy scrambling. You can access the ridge from either end, and either side. There is a good manned refuge (Poquiera), plus several good and some poor/ruined huts.
Winter climbing is a different matter, but the rock to me seemed crap for proper rock climbing up on the ridge and I am not sure of any 'real' rock routes up high. Richard at 'Spanish Highs' (google 'em) is on the spot and will know all the answers
HTH
Chiz