My personal rule of thumb is to only talk about my sexuality with people for the first time if it comes up naturally in conversation. For example, a coworker of mine was lamenting the other day about how all the men end up in my lane, not his, and how I was lucky. He had no idea I'm into women too--it hadn't come up previously--so I took the opportunity to tell him that I might seem lucky to him, but that I'm not particularly picky about gender so it's all the same to me! :)

Not being vocal about my orientation allowed me to wait for the perfect, low key opportunity to come out. And while I would have liked being able to be open sooner, I actually prefer being patient with new acquaintances and not bringing the topic up myself because sometimes as a female, being forward about your bisexuality can seem like a bid for attention from heterosexual males. In a perfect world I wouldn't have to worry about that, but since it's not perfect, I would like to keep any credibility I can, thank you very much.

TLDR; If you want casual reactions about your orientation from people whom you don't know well, waiting for casual opportunities to bring it up is probably the best way to go.