I have day sailed around Havre de Grace and there is local sailing (just below the bridges) if all you want is to day sail and get experience on a boat. But you have to take a captain, as they will not let boats go out single handed. I have chartered out of Annapolis and I took a captain for a half day to confirm my skills, but still there were two of us to charter the boat for the weekend. I would look for a local club to join as they often get better rates and you have a group of people already to sail with. We have done that out of Rock Hall and that worked very well and was economical. There are marina's above Rock Hall in the Bohemia and Sassafrass rivers that you could look up for chartering as well. Sailboat experience requires motoring experience as well so having to chug for an hour out a river is not so bad, plus you need experience docking, fueling, etc. So any of these areas could work for you.
I took the ASA courses but cannot comment on the difference between locations, mine was a long time ago. Also, I took the coastal cruising course in the BVI's and that doubled as a vacation, which was a great time.