There will be students from across the country running around in circles and jumping long and high and often. At night people come out in droves and fill up Sixth Street enough to make SXSW crowds look like a stroll in the woods. (Not really, but kinda.)
In what is possibly the convergence of a really rad apocalypse (at least one that I support), there will be yoga, goats, and beer, and quite possibly the end of the world. Bring your yoga mat and bottled water. Highly recommended.
For those looking to learn more about Austin and get some exercise at the same time, this might do the trick. Choose the type of run, the mileage, and when you'd like to do it, and they'll handle the rest. Advance purchase required.