Back Creek is a favorite anchorage during the boat show. You could anchor near Bert Jabin's, which does get water taxi service that would take you over to the show. Actually, I think you could call the water taxi from anywhere in Back Creek. There is also a large anchorage area near the Naval Academy athletic practice fields, but this is so close to the boat show itself that you may not find any room. The water taxis also work this area.
As far as slips go, there are several marinas in Back Creek--Mears, Annapolis Landing, Port Annapolis, and Bert Jabin's. You might want to contact them now to reserve a slip. Horn Point Marina is directly across from the boat show. There are marinas in Spa Creek north of the drawbridge that connects Annapolis and Eastport. I am not that familiar with them.
Here are some web sites with marina information:
Here is a web site with car rental information for Annapolis: