You definitely won't go wrong with Ciclo Montana. Check out there website and have a look on You Tube - there's a few vids.
Run by some great people in a nice location, the accomodation is nice with a pool & decent workshop area overlooking the hills, the food is decent & plentiful, there's a decent amount of Cafe con Leche stops for chilling etc.
The first ride is a general trail ride to suss out everyone's abilities and then from there the trails are pretty well mathced to your abilities.
The first year I went, the most I had tackled before was Welsh trail centres along with one trip to Glentress/Innerleithen but I found the riding fine. Sure there were plenty of bits that I couldn't do, but it was great at improving my skill level.
Just remember to take plenty of tubes or go tubeless, as most of the Spanish vegetation is pretty spikey & unforgiving on tyres.
They are based in quite a rural location though, so if you are looking to go into a town in the evening for some night-life then you might find it lacking. There is a bar up the road though and to be honest, I am always so tired from a days riding that watching the sunset with a beer and some light bike fettling is all i can manage.