Tickets are now available right up to the end of January 2017 for walking the Caminito del Rey.
There is also now a guided tour option on the booking page and as all the information is in Spanish, One must assume that the guided tour is in spanish as well.
Presumably the web site and the guided tours will be correctly published and supplied in at least English in the near future. As of now it seems the emphasis is on the Spanish language even though a large proportion of visitors are international.