Polyamorous relationship

I'm currently in an open poly "relationship" (I put quotes because we don't call each other boyfriend, girlfriend but if I so choose I can introduce either or both of them to strangers in those terms). 

When I say that we are open I mean that we are all permitted and even encouraged to go on dates/meet members of the opposite or same sex (We're all bisexual, it's like a dream come true) but we don't necessarily bring people into the relationship. 

I'm still fairly new. I was brought in by the couple at the center of it all, I had met Her over the summer and was introduced to Him a few weeks later. They're both precious to me and I to them. However, we each recognize that this is not a relationship likely to last more than a few years. We are all ambitious, highly motivated people, none willing to give up our careers or aspirations. We will of course though, remain friends for a long time. 

My question: how to I broach the subject of my relationship with an outsider I am interested in? If someone rejects me on no other basis than my relationships past or present, then clearly they're not compatible with me anyway. I'm very comfortable in the poly lifestyle, and see it as part of my life for years to come if not into perpetuity. I don't live with my current partners and do not envision myself doing so with any partners in future (I crave independence and privacy). With these considerations in mind, at what point do I become obligated to disclose the details of my lifestyle, relationship status, etc.?