Try calling the Annapolis harbor-masters office first. They can give you good info for moorings and anchoring in and around Annapolis.
The last few times I sailed to the show, I anchored in Weems Creek, on the Severn River. Always room to anchor, and if you get lucky, there may be an open USNA mooring. They're FREE. About 2 blocks from the dinghy landing is the USNA stadium, with free shuttles to the show. Very nice.