Can たち mean "and the others"?
I know that たち is a pluralizing suffix: 私たち、子供たち、etc. But I'm listening to 2 people talking about Mary and her friends. I am confused by how たち is used here.
It is some what similar to an English word 'lot', it's not a formal word to use, but it's not impolite either. 'When are you lot going to Kobe?' is what it sounds like, but bit more polite than what English sounds. If you want to be very frank and quite impolite you could use 「〜ら」, and in formal scenes 「〜方」.