From the archives.
It turns out that your neighbor on the plane/bus/train (or the person sitting at the next table at the coffee shop) is a very, very chatty tourist. Do you try to switch seats, go for a non-committal brief small talk, or make this person your new best friend? – Source
It would depend on many factors. My mood, the conversation’s topic, and stuff like that, but I’d try to be polite, I would stay on the small talk.