How far in advance can we make reservations to take the english-language tour of the Font de Gaume cave?
If you are planning to try by phone or email as Terri Lynn suggested on your previous thread, then just go ahead and do it. The situation is subject to change at any time, and the official English web site discourages this option, probably because they are not booking tours in English via this method. However, any reservation is better than no reservation.
According to others who have tried, they are booked through Oct 31 2015. There are only about a dozen tickets available for reservation a day and it is a high visibility site.