Passing By

It's a 15 minute walk from the MAX station to the PSU campus. I've been walking to and from school for 5 years now. I've walked at the butt-crack of dawn, and I've walked at 9:30 at night. The people of Portland are so different from the people in my suburban town. They are more eccentric, more wealthy, more broke, more rude, and more accepting, depending on who you walk by.
I may be a bit on the paranoid side, but I get so uncomfortable when a man (any age) walks by and stares at me until we pass each other. Sometimes they smile a big toothy grin, and their eyes get really wide, like I just jumped out of the bushes and shouted "Happy Birthday!!" to them. I tend to keep my eyes forward, pretending we didn't just make eye contact.
Then the person may decide to say something, just as we pass each other. It's usually something like "How you doing?" or "Hello." Totally innocent sounding, right? But when you put the creepy grin and the lengthy staring with it, it all gets uncomfortable and my answer is usually different depending on what time of day it is, how many people are around, and how creepy the guy is. Sometimes I just pretend I didn't hear them.
But there ARE guys out there that can pull off a "passing-by-smile" and not make me think about how fast I can get to my pepper spray. It's just a simple 2 second long smile proceeding a simple 2 second eye contact. It says without words that "I acknowledge your existence and appreciate this brief moment that we have walking past eachother." It'll even brighten up my mood sometimes.
Do men encounter this problem at all? This is a daily thing for me. I assume for guys it would not so much be a creepy problem as a "Could this guy beat me up?" kind of a thing. I don't know.
Maybe I'm just paranoid.