I live in Colombia, and in the town where I live, most of the adults and old people often like to start talking to the person who is sitting next to them, and have a nice conversation on the bus trip.
However, I think it depends on every person. My mother often likes to talk to the person who is sitting next to her on the bus, and it's normal for her.
I don't think that I'd do it sometime since I'm not get used to doing it. If someone start talking to me on a bus, I'd not feel uncomfortable, it's not a problem, but perhaps I won't carry on a real conversation.