I am a woman and work in Boston as an engineer currently programming web apps for a consulting company. I had plenty of good experiences but also had a couple of bad ones. I could always catch something during the interview and or when you walk in. I would first evaluate the employer before I evaluate the team. You will need to find an employer that think highly of women. The founder of my company relies heavily on another female leader. Half of his staff are women Another CTO that I work with only has one full time staff female support person and he relies heavily on her. On the other hand I went for an interview where there are no female engineers and the vp of engineer was suffering from unconscious bias. I later heard that other male employees actually disagreed with him for not hiring me. There was another guy that changed his mind half way through during the interview. You will catch it but if there are no strong female leaders/female staff that are heavily relied on then you probably shouldn't work there.
Somebody also has to be the first strong female employee in any given company. Obviously headcount is a huge factor here, but in isolation I honestly think that kind of reasoning can be misleading.
If you are interviewing and discount an otherwise promising potential employer out of hand for not having enough women onboard already, what can they do to rebalance the situation beyond continuing to bring a diverse range of solid candidates in for interview?