AA Center is owned by the City and leased to private entities.
Texas state law says that property owned by a government entity cannot post the signs.
However, the DA in Dallas has put forth the argument that the renter can make that decision since they are in control of the property during the event.
They tried this with the State Fair also and backed down, but it seems no one has challenged them on AA Center.
I think it's BS but basically the posting of signs is case by case. That said, I've never seen them NOT post, and they do have metal detectors.
The only way to be sure is to either find someone to call or go and see for yourself.
Also, would this be considered a "professional sporting event"? That is not defined in state law so....they may use that angle to prohibit carry anyway (those are already prohibited places).