The Camino Schmid is the easiest (in the summer - it's dangerous
in the winter for novices) and one of the most beautiful trails
to walk in the Sierra of Madrid. It's a bit like the Gran Via
for traffic on the weekends so you shouldn't have much of a
problem asking for directions or help. (My Orange cell phone
had coverage there, by the way.)
If you don't have a car, it's no problem as you can catch the
Renfe train out to Cercedilla and then another little train
up to Puerto de Navacerrada. You can walk from there up to the
trail head, which shouldn't take much longer than 15 or 25 minutes
or so depending on your speed. Obviously, you can park much
nearer to the trail head if you drive and you can get to there
faster in 5 to 10 minutes.
A view from the parking lot north towards the province of Segovia.
Towards Rascafria
Towards the ski-lift and the trail head.
If you can find it on a map, that's the "Bola del Mundo"
up there. Those are all ski slopes. The train station is about
10 or 15 minutes to the south (the right).
By the way, this is the Puerto de Navacerrada (Navacerrada Pass).