It really depends on what your goal with the joke is. Is it to crack a joke specifically about Bauhaus for people who already know of them? Or is it to make as many readers as possible laugh?
If it's the former, keep it as is. If it's the latter, perhaps consider changing it? If your test-group all liked the joke, even without knowing who Bauhaus are, I think you might get away with keeping it the way it is, and just adding a link to a wiki-article about Bauhaus or something in your author's note. I mean, if the test-group laughed any way, you've got a good joke.