At scientific conferences. Conferences are not only reports and lectures, they are also a lot of communication. Moreover, this does not necessarily depend on how "exciting" science itself, experts on nematodes can anneal quite at the level of theater experts.
From my own experience, debaters are one of those people with whom you can chat about almost anything, moreover, they are quite open to communication. It's easy to find them, most universities have debate clubs, try going there :)
In general, there are many options, I will name one - events organized by libraries. There you can almost always meet interesting people among the public.