I mention it on my profile, if someone didn't read my profile, but is talking to me like that, they are a shallow person I don't need anyway. I will however, at some point likely bring it up if it is never brought up in the context of my own history just to show whoever I am talking to it isn't something that I am ashamed of or afraid to talk about, more of a "I am trans, what of it?"
That being said, it is quite likely the people in question know about it but, don't want to be the first to broach the subject, I mean after all, it is a pretty personal thing. I know from my own experiences that when dating people who aren't trans they tend to be on eggshells around the issue until I show them I am comfortable with acknowledging and speaking about the fact that I wasn't born as I am now.
So, I would just make a casual mention of an event that makes it clear you are trans, and suggests how willing or not willing you are to talk about the subject. Like set the narrative for your potential partner, and then you can control how the discussion is framed.