Well, let's see.....
Since I actually live in CT, maybe I can offer some random opinion on this matter. I have not taken lessons at Eurodance in Stamford, however, it is run by a well respected and accomplished professionals worth checking out at least. Ballroom Elegance in Westport is home to Vladimir and Irina Gorshkov, well accomplished, experienced, International Standard competitors. I have not taken lessons there, but I have taken a lesson with Irina before. Well worth the investment. I think it's definitely worth checking out for Standard. Ballroom Fever in Enfield is home to Gunnar and Darryl Sverrison, accomplished professionals with years of experience. It is a bit far (Enfield is on the Mass. Border), so I cannot comment on what it's like there. Ballroom on Fifth is probably the most popular place to go for standard in the tri-state area and is home to several world famous coaches. Rogers Dancesport in NJ is home to Gary and Diana McDonald. Another excellent school.
Friendliness of students is something that can only be answered by you. When I evaluate the social atmosphere of a studio, I'll go to one of their socials and judge for myself. As far as studio "selling", it can be annoying, but you can always just say "no thank you". As far as quality of instruction, I've always found that to be a combination consisting of the instructor, and you.
In addition to the previously mentioned places, as well as Stephen and Larinda, feel free to add the Fred Astaire in Norwalk and the Fred Astaire in Bardonia, NY. The Norwalk studio is owned by Martin and Gina Goethe, accomplished European 10 dancers, and has a friendly social atmosphere. I have taken latin lessons with Gina, well worth the investment. The Bardonia location is home to Victor and Natalia Russu, accomplished European 10 dancers as well as American Smooth competitors. In the past, I have worked with both Victor and Natalia, and I know I certainly learned much from the experiences. Franchises, yes, but individually owned and managed. You'll probably get a sales pitch, but again, you can always say 'no thank you'. I generally say no to the pitch and focus on the learning. You have many more choices to consider(especially if you're willing to go into NYC!), I would recommend trying them out for yourself and making a decision that is right for you.
I hope this helps.
DISCLAIMER: These are my own opinions and mine alone. I do not work for any of the previously mentioned studios/instructors and I have nothing to gain by mentioning them.