Quote Originally Posted by zorro View Post
One of the characters, Kolya, says "Ну что ж, пошли", which on the English side says, "Well, let's go". Can "пойдём" also mean "let's go"?
Yes, it can: "Ну что ж, пошли! = Ну что ж, пойдём!"

I've only learned "пошли" as a past tense form so far. How does that work as "let's go"?
In colloquial speech, past tense forms of verbs of motion are often used to express an invitation to go together (like пошли! поехали! побежали! полетели! поплыли! etc.) or a command (note - if a command, it sounds rude): пошёл вон отсюда! (go away from here!) etc.

Usage of past tense intensifies the imperative sentense (as if we are half a way already to get something done).

Note. Although it can be used with other verbs sometimes, the most typical usage of this form is verbs of motion.