I can relate, and I struggle with it terribly, because someone can say something to me, then i'm fighting in my head what I should say, or when the moment has passed I think of things I could have said.
I'm currently a delivery driver for a big car parts company, most of my time is spent on the road, but there is the time in the morning, and a small amount of time I spend in the warehouse in between my runs and the talk that goes on does not interest me whatsoever. I work with a mixture of people, old, young, male and female and mixed race.
Its either what they saw on TV, sport, an outing to "town", mugging each other off, swearing at each other, talking explicitly about someone of the opposite sex, drugs, etc, all the things that have no relevance to me, so I usually just smile and agree.
Then when I meet the people at the other end of where I am delivering, to the other branches, I usually say good morning and hello through out the day, hows things, and then its just people complaining about their jobs, and then I feel even more awkward when I say hello or see you again and I get no response! I just seem to get odd looks when I'm greeting people!