We stayed at a great small place on the hill not far from the castle - super location for exploring both sides of the city, and quirky-yet-clean rooms and a friendly reception. It's called something like U chernova lva (means at the red lion, even though for a Russian speaker, it seems more like it should be black lion!) It was medium priced and good value, and gave a feeling of really staying in the city (stayed at the Marriott once, on business - very nice, but very Marriott). You'll do ok with English and the Russian will help decipher some of the Czech slavic-based words and a lot of the population will speak some Russian, but, like the earlier post regarding German, the Czechs aren't too fond of the Russians. As for must sees, this is one of the best walking and wandering cities I've ever been in, and I could also recommend you find a good marionnete theater, as it's quite an experience.

Enjoy!

(PS: of interest/amusement to Russian speakers: the "pozor" signs you see all over the city are "caution" signs ...)