I'm one of a four person writing group that formed in 2004 when a friend suggested it to a friend and she brought her friend.
Even though we focus primarily on fiction and poetry, one of our four is an English prof who has written extensively in non-fiction - including articles for Facts on File, a Feminist analysis of the Harry Potter series, and several other large and small projects.
As we all have a background in English with various experiences in journalism, teaching, technical writing, and/or Women's Studies, we welcomed her non-fiction projects into our group. We gave her advice on just the sort of things you're looking for - organization, presentation of arguments, language level/word choice, and other various aspects of non-fiction.
On the other hand, writers are a naturally insecure bunch and may feel uncomfortable with someone of your background and experience joining their existing group. Plus some writing groups really get hung up on their primary focus (Romances, Mysteries, literary fiction, etc) - establishing hard goals and bragging about the number of published books they have. They will have no interest in anything outside their chosen genre.
My experience tells me that, short of a warm reply from an existing group, your best bet will be trying to create your own writers group that isn't an hour away - maybe recruiting members out of your peers and friends (or peers' friends). The riskier path might be to make a bulletin board posting at your local library or coffee shop (or wherever you're likely to find the kinds of writers with the background you're looking for).
You might also want to try posting your call to form a group in an online writing forum like the Absolute Write Water Cooler -
http://www.absolutewrite.com/forums/ - or Writer's Digest's online forums, not to mention so many more. There you may be able to find people serious about writing in your area. Or, better yet, you may find an electronic solution to your writing group needs.