I met my SO when I didn't want to date, I had the intent of making friends and staying single. So the conversation didn't get brought up until he told me personal stuff about him and how he had family members who went through the same kind of trauma i did. It was around a month of just hanging out when i told him and despite that information about me, he still wanted to pursue a romantic relationship. I think if I was in a situation where I was looking to date, I would tell them right away. I wouldn't go into full detail, but I would explain that I have PTSD and answer questions I'm comfortable sharing. I think if they couldn't accept that, then they weren't for me and it would weed out the people that just wouldn't work out anyways. That being said, it's not something that would be easy to do and can be uncomfortable, but in the long run it would help in finding the right person.