This stretch is mostly gravel and the views are spectacular. The climb is steeper if you come from Espinama, so I'd recommend following the route from Sotres to Espinama instead. Vehicles are restricted and therefore the road is quiet. Do watch out with loose gravel since some stretches are pretty steep and you might be better off by pushing your bike.
At the top, you can find the Hotel/Cafetería Áliva were you can spend the night or eat something. Since this is a National Park, it's important to respect the landscape. Water can only be found at the/near the hotel area.
There is also a funicular from Fuente De and you can bring your bike along in certain times of the day. You can skip the tough climb from Espanima by taking this funicular.