Agree with most others, where you live depends on how easily you feel you can get around/reliability of vehicle. The light rail system makes it such that more areas are available without needing to drive, but it can be slow and sometimes crowded. I've lived on the south, south end of Tempe and commuted to ASU every day...no big deal. It takes about 15-20 minutes on surface streets in average traffic, but it's an easy drive.
I'd recommend something in the Tempe area, and I think the "danger" lies somewhere between Gaud and Nammertat. Most places are pretty safe, but make no mistake, it can get weird in Tempe, there are definitely some dicey areas. You may consider San Marbeya, Archstone, the Vue, or Grigio. Those are all on the higher end, though, so a roommate might make sense for you there. I'm happy to help with apartment/area suggestions, I've lived in Tempe and been to almost every complex in the area. Yeah, I'm a lifer.
There's a covered parking garage with lots of space across the street from the law school buildings. You'll find after a few weeks in Phoenix in the summer that parking in the shade trumps proximity almost every single time. Parking in the garage for a whole year (Aug-July) should set you back about $800. Pricey, but worth it. The stadium and arena lots can be had for much less, but I wouldn't do those without a bike. ASU is a large, sparse campus, and it would take close to 20 minutes to walk from those lots to the law school buildings.