Several years ago a friend of mine used the yellow flowers as bittering hops as an experiment. The beer turned out pretty good. However, there was a subtle off-flavor that wasn't necessarily bad, just different. The same guy also made a beer from kudzu starch. That one wasn't bad either. I think he went pretty easy with it.
As for the polkweed salad... if you don't cook it correctly, it can get you very sick.
