they honestly know they look alike they just assume they look the same. they've seen them both on numerous occasions. I think a bigger issue is no one cares, to them he doesn't hide anything so they might think it in their head but never ask.
Gender: Male Location: Drinking gasoline. Pissing napalm.
Do you happen to know the comic (it was in the PC era I'm pretty sure) where Clark is looking in the mirror, putting on his glasses, and remarking to himself how absurd the disguise was? Something to the effect of, "This is stupid. I don't look like a different person. I look like Superman with glasses. When someone gets glasses for the first time, no one says, 'Who is that guy?' No, they say, 'Hey so-and-so got some new glasses.' I'm not going to fool anyone like this."
...I'll try to find the scans later, still don't know the comic they came from though.