February does seem to be the time of semester when the winter ASL students get their first assignment to talk to a deaf person.
My rule of thumb, if they don't say right away, they are most likely hearing people.
On that topic, today in Target with my husband, I got really close to an old guy also looking at toothpaste. As he saw me and skittered away in horror, my husband noticed his CI.
I decided he must be a formerly hearing implantee and has had terrible experiences when deaf people saw him and tried to sign to him.
Either that or he just recognized me and was terrified...