For the faint at heart, the weak-kneed or the elderly, visiting the castle is a bit of a trek. First you have to march all the way from the train platform to the village below the castle (assuming you didn't come by car), and then you have to march up a winding hillside to reach the castle gates. This is enough to wind most travelers who aren't even tired or infirm, so by all means have comfortable shoes and expect to climb in your castle exploration.
Don't try to take a photo or bring a camcorder within the castle. Sensors pick up the use of electronic equipment and will bring the police promptly. As a storing facility for priceless relics, the security is well-suited to prevent interested parties from casing the place and planning a heist.
The guides speak both Czech and your language, but I doubt they would serve as a strong advocate, who likely will not speak your language.