Me and my partner's kind of code phrase for me going off to AA (if we talk about me going to a meeting in front of others, or a non-close friend or acquaintance asks where I am / I'm going) is 'going for a coffee and chant with some friends.'
I tend to feel that's pretty much as much as they need to know.
I wouldn't tell someone in that situation. IF you end up living with them, and they become a trusted friend then maybe consider telling them then.