I haven't heard of this hostel, but the best place to stay is this place called "Hotel Europa". It is a beautiful old Art Nouveau building on the main strip. The regular rooms are probably expensive, but there are smaller side rooms (which I believe were in past times servant quarters) that are cheap. I happened upon this by chance because someone from the hotel was recruiting in the subway, but I'm sure you can scout it out. Watch out for most hostels in Prague, because they are often not in the central area and require an annoying commute. If you can, I would suggest changing your plans, nothing can beat this place.