Yeah nobody shows up to a party sober. I know last year we'd start drinking like 3 hours before the fraternity parties started (bands usually start at 10). Now that I live in the house I start a little later since I can just go up to my room and get more alcohol, or if we have house alcohol I can get that.
(except game days when I start around noon)
edit: bands usually start at 10, on game days a lot of houses will also have an afternoon band which starts when the football game ends (4pm)