My biological mother had bipolar disorder, as they called it back then. I don't really remember any episodes with her, but after I was 7 the only times I really saw her were when she was on medication, perfectly lucid but shaky as hell (this would be early 90's). They never did get the right meds figured out before cancer interfered... I'm not entirely sure if she was still on them once the chemo started but she seemed a lot happier at that point. Maybe it was just because she was getting to see her children.
In high school, a friend of mine had manic-depression (as they call it now, since, obviously, she still has it... I just haven't talked to her since graduation.) I witnessed a couple episodes- the dorm mother was very bad about making sure she got the lithium she needed. The first year, the way she explained it was she got enough to keep the mania in control, but not enough for the depression. I talked her through the depression, completely missing the "back to your rooms" bell causing panic in the dorms because they all knew I wouldn't run away. They were trying to figure out how the hell I could've been kidnapped.
Second year, she just didn't get any of her meds. Maybe once a week or something. So, I witnessed a couple episodes that year. She scared me when she was manic (she tended towards the bloody), but I stayed until she asked me to leave. I know she was glad that I did, and at the same time didn't think the same of me afterwards, though my view of her didn't change.
At the gas station where I worked, there was an older gentleman who ended up having a couple long conversations with me during some very slow nights. Turned out he had manic-depression. That didn't phase me- the bit that I found creepy was his tendency to start flirting... but I know that had nothing to do with the disorder that was on his medical records.
So, yeah, as long as you are on your meds, I'll treat you like anyone else I know. If you weren't, and you were depressive, I would make sure you weren't suicidal before I left. If you were manic, I'd still chat and laugh with you unless it looked like you were about to get out of hand. Otherwise, still, treat you like anyone else. (Which, yeah, I'd do the same with anyone else having a nervous break-down or a really bad day- stay with them until I knew they were okay or it looked like I might be in danger) For the most part, I won't think about it while you're in my presence; though I might try to dissect the encounter when you were gone, I'm tactful enough that I won't tell you about that part. Don't take it personally- I do that to everyone.