Firstly, xbikes is a great shop. The man there, I think an ex-pro, is very very good at what he does and is a nice guy too. If there was any chance of getting out with him and his friends on an mtb it would be a real cultural submersion as well as great riding. That said I don’t know if that is possible and haven’t looked into it myself as I am always on the road bike when in that area. The other thing is there has been a lot of bad weather there this year and there might be storm damage to the trails. So, road bike: amazing. The N340 in both directions from nerja (west flat, east hilly) is a great start and impossible to get lost on. Then, next step up, I would consider a route up to somewhere like frigiliana or Competa or one then the other. At the other end of the scale would be a really big day out like up to ventas de zafarraya via the back of velez malaga, or, in the other direction, the stunning ‘goat road’ out the back of Almunecar.