When I pass someone riding in the same direction as me and I say "hi", 95% of the time the other person will respond similarly. This applies to all demographic groups on my local roads.

If I pass someone going in the other direction on the other side of the road, I would hope that their number one priority is saftey issues on their side of the road. Greeting people 2 or more lanes away from them should be pretty far down on the attention list.