Well that's extra harsh, if one of the people you can't tell is someone you're interested in. I don't suppose there's any back-door way to approach this? Such as chatting with her about a show about polyamory (e.g. Showtime's "Polyamory: married and dating"). Maybe you can get a philosophical discussion going without admitting your own polyamorousness.
I definitely recommend searching for a poly group in your area; I think it would be good for your morale. This site is nice too, but there's something about being able to talk with people in a live setting, who you don't have to worry about shaming or shunning you.
I hope things work out for you somehow.
Love means never having to say, "Put down that meat cleaver!"