Some of the posters have mentioned Courageous and The saling Center. Another is: http://www.bostonharborsailing.com/
Any one of these would be a wise choice if your not sure what you want to do. The saling club near Rowes Wharf would allow you to sail a variety of boats. This would help you understand the key characteristics that you seek. I was a member there for a number of years in the early 90's and now have my own boat in the Shipyard at Charlestown. The club is a no hassle relatively low cost access to boats that would allow you great access to the surrounding waters. While I was there I pretty much sailed whenever I wanted, sometimes 6 days a week.