Inside the tourist areas you won't have a problem finding people who speak English. Just a few phrases to help you along.

Mluvíte anglicky? (pronounced "MLOO-vee-tay ON-glits-skee")= do you speak English?

Nemluvím česky ("NAY-mloo-veem CHESS-key")= I don't speak Czech.

Jedno pivo, prosím ("YED-no PEE-vo, PRO-seem")= one beer, please