Each Border's is in charge of their own events. Don't bother calling the corporate office in Ann Arbor. I know people who've played at a number of different Borders stores here in the Seattle area and it's always handled by the store itself. Some stores are better equipped (physically and staff-wise) for handling live performance.
I also used to work at Border's corporate office in A2 waaaaayyyyy back when and know that each store has their own local events co-ordinator for handling author signings, community events, etc. Perhaps someone in that position could be the most helpful (or the store manager of course).