FWIW, IMHO, AFAIK, IIRC, I called their toll-free number just for the heck of it, and its recording was excruciatingly condescending. Basically, It's smart of you to call us. I can't bear to transcribe what the voice actually says. It's in a Boston accent, too.
There's plenty of other places to find smart people's clubs, like chess clubs. If you want my opinion.
Remember an old Bob Newhart Show episode where his wife, Suzanne Pleshette, is a Mensan, and they go to a meeting and the Mensans are all... rather strange, shall we say?

(I suppose I cheated a little with those acronyms up there but I just wanted a chance to use four acronyms in a row. :) )