I didn't mention it to dates/potential girlfriends until I had a fairly good idea that we were going to be seeing each other a while. I didn't want to come right out with it in case it scared anyone off. I wanted them to get to know me first, for who I am, then drop the bomb. I can honestly say, I didn't have a single one that had an issue with my telling her. Of course, a few of them had issues with my behavior later, but you know. That's probably my fault for being an unmedicated mess most of the time.

Take your time and get to know someone first, before you tell them about your diagnosis. It's hard to really gauge how a person will react, but try to get a good idea of the type of person they are first. If you can tell they're a person who is not going to overreact and presume the worst, tell them and take it from there.