I'd recommend Stonington, particularly pawcatuck. That's the area I live in. Mystic is great but is very, very crowded in the summer. Pawcatuck is right next to Westerly, Rhode Island which has a great downtown and is way less busy than Mystic. Stonington Borough is a very nice, old school new England neighborhood with some lovely restaurants but the age group there is a bit (ok a lot) older than you. There is quicker access to beaches from Stonington/pawcatuck than towns west. Not sure what your outdoorsy interests are but it's a great area for fishing, there is good hiking close by, and judging by the number of cyclists I'd say that's a great option too.