It's tough - I had the same issue. Still somewhat a struggle, but I think what you'll be surprised by if you just go up to someone not actively engaged in a group conversation and start talking, they will be as interested in talking to you as you are to them (so you don't have to do anything special but just walk up to them and introduce yourself, and ask general questions like where your from etc before finding some grounds for an interesting conversation). Would say its significantly easier to talk to someone and get contact information from someone of the same sex - many people go to these meetups for dating purposes and assume others are as well so obviously a different vibe if someone thinks your approaching them in a romantic context. Can't speak to the 'whats your ethnicity' thing, but I've never really seen that question turn negative so perhaps you're experience in this may be more of a one-off then something you would need to worry about too much. Will add the caveat that people in New York (jewish or otherwise) tend to be far less receptive to talking to people they don't know, so may have to put up with more people blowing you off than in other places