It is easy to book a room on Priceline. I paid $63/night at the Hilton Old Town, and it is right next door to the Czech Airline office with a 130 CZK bus to the airport. I would not want to spend the time going into the city during the day, and suggest staying in town instead. The walking in the Old Town vicinity is safe and other posters are correct in saying that the night views are spectacular, and different from day views. Crystal shops like Erpet are open late (10 or 11 PM). There is a little show at the Astronomical Clock every hour on the hour. And the square is bustling until at least 11 or midnight! The airport is ~ 30 minutes away from Old Town.