I have. It is right next door to the Wyndham Hotel (I think that's the name) which across from River Walk.

We used it when we went to a car show which was inside the convention center. We had more than the required 1/4 tank minimum, so they told us to go "burn it off" there. The long sweeping turn is banked and the straight away is about 1/4-1/2 mi long. I know it was marked off for the 1/4, although fast cars would have a little less room to slow down before entering the big sweeper.

Admin aka Paul was with me and he can attest to it. He drove our friends stock Accord and had it screaming around the turns.

It's a super awesome place since it's just a deserted track, although last time I was down there they had concrete barriers blocking the entrance.

So in short....it certainly does exist and I enjoyed the heck out of it.

Great find. +1 for you.