I've told a few people. I don't think the issue is as black and white as express your ABDL side or repress it. It depends on who you open up to - and should be judged on how open-minded, understanding and trustworthy you believe them to be.
I told my former caregiver. She had a little side too, so that was just very fortunate. Even after we stopped talking (for totally unrelated reasons) and went our separate ways, I don't think she's told anyone else about my tendencies, and same vice-versa. I told one very close former female friend. She found it a bit confusing, but had no issue with it per se, just saw it as a quirk.
My Dad and one of my brothers have an idea that I sometimes like to act like a kid when I'm stressed out, but probably not the regularity with which I indulge my little side. Both of them think it's a bit odd, but accept it and attribute it to a coping mechanism. I'm not certain that it is, but if the worst thing they think about my ABDL is that it's a pretty harmless emotional crutch, it could be a lot worse.