In reply to James58t:
It's worth getting the Cicerone Walking Guide. I think the best walk I have done was Walk 1 from Santa Cruz and up Barranco de la Madera coming back down via the the tunnels cut through the cliff face of the Lomo de las Nieves is well worth doing. Very varied quite exposed in places with stunning views. Take a head torch for the tunnels, quite low roof height in places, we didn't take helmets, but if you've got them it saves banging your head in places!! The full 19k from Santa Cruz and return, is a great day out, or you can shorten it by taking a taxi up to Las Nieves (the church here is worth visiting, and you can get a beer or coffee in the village square at the end). That reduces the walk to 8k if you get the taxi to meet you again, or 11k if you walk down to Santa Cruz.
Walk 26 is a good 19k circular. you can start either at El Tablado, Franceses (where we did) or the cafe at Roques del Faro. . The way we did it meant we had to cross the very deep Barranco de los Hombres at the end of a very hot day and the climb back up to Franceses was knackering, but well worth it. Probably better to do this earlier in the day by starting from El Tablado.
You can do sections of the GR 130 along astoundingly beautiful North coastlines with much up and down crossings of Barrancos, but these are linear, so you have the problem of getting back to your car at he end of the day. We were B&B ing which made this less of a problem, but accommodation up there is sparce and you must book in advnce.
Enjoy! I'm quite envious