In reply to Joint: 2 of us took 10 teenagers and 1 inexperienced adult through it in Feb 2011 (Pics here:
http://alanhalewood.blogspot.co.uk/2011/02/canyon-dinfierno.html ). Well bolted, plenty easy scrambling and lots of abseils/lowers. There is 1 traverse that when we were there was equipped with a frayed fixed low stretch rope (second pic shows me adding our rope over it). This was strenuous and I had to hoist / help a number of the group up the start and onto the finishing ledge.
The walk out was a little hard to find (keep going, its further than you think) and then a steep pull up.
From memory fit teenagers / a little younger if used to climbing and hillwalking should be fine. Much younger / less experienced may be a little much.
Great canyon. In feb we had 1 knee deep wade, the rest was dry but I have no idea about water levels at this time of year- worth checking with locals. There is a warning on this site (good directions on how to get out at the end:
http://costablancaclimbing.com/canyoning.html ).
Good advice from the Orange house here
http://theorangehouse.co.uk/online-topos/barranco-del-inferno and a video here