Last year was my first-ever Hot Air Ballon Fiesta, and though some of my expectations weren't met, I must say that I had a great time looking up in the sky watching our brave pilots fly in the air like some superheroes.
There were really a lot of activities to watch out for, so if I were you, you should also be there earlier so not to miss anything. And for your reference here's the schedule of this 4-day long flying extravaganza.
(read my entry on the 16th Hot Air Balloon Fiesta)