Thank you for the welcome. We are not really that far away from each other. We should be visiting St. Louis sometime this summer as I have family that lives there and daughter is having a fit wanting to go to the zoo.
I was just there today! I LOVE the St. Louis Zoo. If you're willing to walk a bit, as far as parking is concerned, you certainly can't beat FREE.
One tip if you haven't been there (though if you aren't that far, I'm guessing you have been there) is to get there early if you don't want to pay for parking. Also, most of the things you have to pay for once inside the zoo (Children's zoo, stingrays, etc.) are free for the first hour the zoo is open, which would be 8am to 9am.