For local/regional, you might try the bulletin board at West Photo in the spring (or call them). Also, Minneapolis Photo Center might have some info/leads. I've never seen anything specific to LF from the local community ed type resources. My fear is that most local workshops will be geared toward digital.
I don't know specifically what you're looking for, but I would assume there would be some demand for a workshop that focused on the elements specific to LF sheet film (camera movements, workflow, development and printing) for those already familiar with roll film.