I strongly recommend you go on an escorted walk from Masca. That way you are shown the safest route, transport to Masca is arranged and the boat is booked for you. It can be a dangerous walk for the inexperienced, as has been demonstrated by the number of accidents (some fatal) over the years. I suggest you look for a leaflet on Tenerife walks at the LG bus stop (and in many other places around town) or ask at the travel shop adjacent to the bus stop. There is an organised Masca walk every Thursday. Even though I am quite an experienced walker, I would not consider attempting this walk on my own and have been three times with this group and thoroughly enjoyed it.