All of them!
Or, try the styles you like first, and then try a few ones that you might not like. We've gone to this fest the past three years and have a blast every time. The booklet they give you has a nice description of each beer and what to expect.
I'm more on the wine/cider world, and being a non beer drinker, I always find two or three that are really enjoyable.
Try to get there early in the day. Once 5pm happens, it gets crowded and lines get long.
A few years ago there was some deal where you pick up the tickets at some radio station. Does anyone know if this is special is going on this year? I can't seem to find any info on it.