If you want to learn a lot about how these horses are warmed up, you can pull up a chair at the warm up arena and get an eye full. Sometimes, it is more fun to watch there, than the round.
What HER said, too. If you go into the indoor, where most of the vendors are, you can watch a jumbotron in the front/near the stage. I am usually scouting for last minute closeout deals, so watch from there.