I finally got a pic of the observation tower. This is from my sister's street in Del Valle. I could see the tower from their front porch. Their neighborhood is only about 2 miles from the track.
I need to get another photo, too. You can actually see the tower and the grandstands really well from Highway 71 just as you're passing the airport.
I should be able to get some more later this month, plus some of downtown from the Expo Center.