Because cabs run on meters, and traffic getting to the arena can be heavy and slow moving, you'd be better off getting a rental car for a day or have a car service take you there and back.  The parking is generally $10.  
With no traffic it's about a 30 minute drive from DTD.  I'd plan on it taking an hour.
Which show are you going to see?  I'll be shooting RHCP and the Nickelback/3DG/Breaking Benjamin shows coming up there.
Anne