Asking at the library does seem like the best idea.
Do you have stores or any places where they have public bulletin boards where people post up little want ads and notices and such? Our local supermarket has one, for example. That might be a good place to seek. And in the newspapers, too.
And perhaps through the school system. My high school started a writing group AFTER I graduated! *sniff*
The last suggestion here of course wouldn't apply to nonstudents, but there's a chance you could speak with a teacher who organized the thing and find out how to do the same for adults, if such a group doesn't already exist.
And check in neighboring towns, if they're bigger/more diverse. (My hometown is quite small but there are bigger towns nearby where there are surely such things as writing groups.)
OH! And bookstores! *slaps head* Of course. My bookstore has a book discussion group so it's not such a long shot. Some bookstores have cafes which would be a good place to meet.
Keep in mind these are suggestions from somebody who has never belonged to a writing group, and practically never leaves the house.
