Question for Americans

I’m planning to visit my sister in New York for two weeks at the end of September.

Now, because having house guests is stressful, I’m also planning to go away for a few days on the weekdays – give her some time away from me. A good friend lives in Boca Raton, so I’m going down to visit her (I have never been to Florida before – I may die from the humidity).

But, having been to Chicago, Philadelphia, Boston and DC, I’m struggling to come up with a place to go for the other week. Admittedly, I’d probably only go for two nights at the most, and I can’t drive, so hiring a car and exploring the more isolated parts isn’t really possible. (I also don’t want to fly to the West Coast – though I LOVED San Francisco when I was there – as the five hour flight/ensuing jet lag isn’t worth it for such a short trip).

Any suggestions as to where might be good?