The booking portal for the Caminito del Rey has now made available all dates up to and including the 30th of September 2015. There is also and English language option at the top right of the portal.
Full information for booking a walk can be found here…
I’ve been living in this lovely area of Western Andalucia for the last 20 years or so and dedicate most of my time to the running of English language tourist information websites for the towns of Cádiz, Ronda, Grazalema, the famous or infamous Caminito del Rey, and also Wildside Holidays, which promotes sustainable and eco-friendly businesses running wildlife and walking holidays in Spain.