Food in the dorms is ok...pretty good for dorm food, but still gets old after a while. Commons has pretty good options, that's why if you can talk your parents into one of the meal plans that lets you spend money anywhere, and not just the cafeteria's youll be happier.
Types of ECs: Greek life(by far the biggest social influence), professional/academic/leadership orgs (usually not all that social, though some are), clubs (fairly social-check out the involvement fair the first week of classes), and your other random college stuff.
You won't have a problem meeting people at USC, if that is what you are asking. I have always found most USC students very friendly and welcoming.