Telling new interests about your "open relationship"?

[BigRedBeta]

So this girl I've been talking to since April and dating extensively for the last 7 weeks (travel schedules and medical school tests intervened for 6 weeks in May and June) and I have mutually reached a decision that we're definitely together, but not exclusive. As facebook would define it, it's an open relationship.

Without getting into the gritty details, both of our recent dating histories (all within the timeframe that we've known each other) have made being exclusive to each other a good thing to delay. For the record, the non-exclusiveness was much more her idea than mine...

My question is this though...if I see a girl in a bar that I hit it off with, how/what do I tell this new girl? I'm usually pretty honest, especially if asked direct questions (got me in trouble earlier this summer). Should I deny? Be very upfront about what my situation is? Use the ole' Mitch Hedburg "I don't have a girlfriend, I just know a girl who would be really mad if she heard me say that" line?

Obviously any new chick I'm probably going to be more focused on hooking up with rather than dating, but if not? Then what?

Any ideas, prior experience, and thoughts would be great...My feeling is why agree to be non-exclusive if I just end up in de facto exclusivity and there's the possibility of her hooking up with her personal trainer for a second time?