iregendwie,
Hi! Keep SMILING! 
I feel the same way you do...I meet with a lot of unsmiling, sour faces. But then there are those 1 or 2 who smile back!
I refuse to take others' unfriendliness personally. If they are sour, they must be having a bad day and need my smile even more. For those few (like a neighbor I have) who just NEVER smile back, never ever...I just ignore them (her).
Keep smiling and sooner or later you will get smiles in return