If you visit the castle, you have 2 choices. Either a ticket for 7 euro (guided tour included) or a ticket for the garden, falconer and grounds (2,50 euro).
Now if you're not sure that you'll do the guided tour, then do not buy the full ticket! You can enter the castle's center court but you cannot visit inside if you do not have the full ticket. However, if you, like me, visited on a day with loads of screaming schoolchildren, the enjoyment of the visit fast disappears. So, with my full ticket, I only climbed the South Tower and visited the ground. I could've saved myself 4,50 euro!
The website says:
"There are no guided tours in the english language however our guides will, depending on the group, be happy to give some information in english. Moreover there are handouts available in english, french, german and spanish which give a summary of the basic text of the guided tours.
There is also an english audiotour, available at the museum shop."
Don't take the tour with the lady with the high pitched voice! With several tours an hour it would be better to wait a while for the next tour to start ...
That's me after the tour in the central court yard.