Interesting topic. I guess in every region you go to there is a different dialect, and if you live in that area it is probably useful to learn how to understand and converse in that dialect. Of course to be able to speak and understand hochdeutsch is important, but if you are just having a conversation with a local person, you cannot expect them to do that just because you are a foreigner. It is pretty much the same in every country really. Sure using dialect can be hard but Schweizer Mundart is important to learn and understand if you live in the country. Mixing between Hochdeutsch and Schweizer Mundart could be very confusing though.

What is interestung, is that on main television programs in Germany they sometimes subtitle people if they do not speak Hochdeutsch, even if it is from a German area. It is hard to understand the dialect if you are not from the area, but if you go and live there, it is most important to learn.