I would be hesitant to plan three months in the Bahamas or
Caribbean during the summer. Odds of a
hurricane over that time period just too high.
New England would be my choice for a 3 month summer cruise. You have all of
Long Island Sound from NY Harbor to Montauk and eastern CT, Block Island,
Martha's Vineyard,
Cape Cod and even
Maine if you want to go further.
Finding a boat for a full season is another matter. Since summer is off season in the
Caribbean you might find some deals there, but that is the entire sailing season in
New England and demand for
boats will be at the max. Of course if you're willing to pay the going rate I'm sure you could find a
charter company to charter you a boat for three months but the cost would be steep. Depending on the size, age and condition of the boat, charters can run a $600-$800/week to double that. Monthly discounts for the peak season would not be much. So for a +/- 40' boat you could spend $10-$20,000 for the season .