I live South of Mesa, so I have about the same drive as you will. Leave yourself about 45 min to an hour and you should be OK (especially that early on a Sunday). Beware that the I-60 has been closed the last few weekends. I suggest that you take the I-10 West to the 303. Take the 303 North to Grand (or whatever it's called way up there). Alternately, you could take I-17 North to Bell road (or even as far as the 101) and head West to Grand. After that, follow the directions on the Speedworld web site.
I look forward to meeting you there.