Bohemia is part of the country where Prague is and with that dialect, you can fare very well all over the country. You'll stick out, and sound downright silly in the depths of Moravia, but you'll be fine. I can't ever remember not being able to understand a Bohemian simply because most TV shows are dubbed by Bohemians.

But if you're a Moravian (like me), you'll be quite unlucky in the rest of the country. Moravians speak quite quickly and in a deep voice. The language in the thick of it is nearly impossible to understand. There's nothing offensive about it, it just sounds like garbage to any person that speaks the proper Czech language.