For me poly is an orientation. But I wouldn't call it a sexual orientation.
As a young teen, I would fall in love and immediately assume that meant the relationship I was in had to end. I didn't know relationships could be conducted any other way. Even after I met Runic Wolf, I was still attracted to several of my female friends. But I never acted on it because I wasn't ready to believe I was bi-sexual and because he truly is a part of me that I didn't know was missing until I found it. Runic Wolf and I learned about poly together and both identified with it, which makes things so much easier in alot of ways.
I prefer to live polyamarously because it means I do not have to deny my feelings for another.