Would it be better to be in a group or alone 2 weeks into a zombie apocalypse?

Really small group, maybe four or five. There's enough people to keep you from going bonkers. The watch shifts would be short enough that you wouldn't have to worry too much about people falling asleep. Small groups can move quickly and nearly as quiet as a single person. You've got someone to watch your back. Plus, in a small group like that, it would probably be a few people who you trust a lot, which is important.