OK. I see people beating you up and you simply asked for advice. Yes, the standard relationship includes 2 people. Yes, those 2 people can live the rest of their lives happy and content with just that. Alot of women feel that the open relationship title is taboo and refuse to talk about it at all. But let me assure you, MOST of them have secret desires for it. So take their "male bashing" with a grain of salt. I am proud and confident in the fact that my open relationship is the best relationship I've ever had, and I'm 37 years old. If a couple is in a true and honest open relationship, there is 100% trust, and chances are, they have better communication than most monogamous couples do. This is 2012, don't let someone judge you for being yourself.
With that being said, yes, you were drinking, and so was she. That does cloud things a bit, but I'm sure she won't forget the conversation did happen. Stick to exactly what you said to her "if it ever was possible, I think she is insanely beautiful (and she is) and was interested, to let me know". Now, the ball is in her court if she so decides to use it. You don't want to be too pushy with it. You've planted the seed in her head. Drunk words speak sobor thoughts and she did tell you they had discussed such an arrangment. It's doubtful that things will happen with you but only because you're leaving in a couple of weeks. At least you didn't shy away from your true feelings. Women love to feel desireable. If nothing else, you gave her a confidence boost.
Continue to be honest with your feelings and yourself. Never regret that. Be proud of your courage. It just may allow you to find the perfect "open relationship" in your new town
Best of luck!