what should I say when I call him though. SHould I just tell him I'm interested in joining the track team or what.
Do you go to Texas right now?
I graduated from grad school at Texas in May and used to hang around the track alot especially with Mario the field/deca coach. I know all of the coaches very well.
They limit the numbers of walk ons, because it does still cost the team some money to have walkons, and they take some coaching time away from the point scoring/scholarship athletes. It also depends on how deep they are at the events you are trying to do. Texas is ridiculously strong in the decathlon at the moment, they have the returning champion, the returning 3rd placer (who is a jr), and a really good freshman hurdler(13.72) and jumper that they are going to have doing decathlon this year.
I don't mean to discourage you, they may let you do it, but the numbers you listed don't sound real encouraging. There are a bunch of distance runners that go to school at Texas that could make alot of good div 1 track teams that they have asked to walk on that they have turned away because the distance team is so large and strong. Just talk to Bubba Thornton (the head coach) or Mario Sategna (the field events coach) and tell him that you would like to walk on to the team. He'll probably ask you about what events you do and what kind of marks you have done and decide from there.