I would be haunting the humane society shelters.
I'll second that. All of the dogs I've ever lived with, including both of our current dogs, have been rescues from the humane society. I think a working dog mix might be a good choice. At our house, Sage is a blue heeler mix and Iris is a lab/border collie, and both do a fine job of keeping the varmints out of the garden. They're both smart -- although Iris has a silly streak -- good with people, cautious with strangers and they're great house dogs, too.