It is the best "Central Phoenix" Dog Park but I wouldn't go in the evenings. The last time I was there all the ladies were complaining about a weird stalker guy who didn't even have a dog but was sitting in the small dog area trying to chat up young women.
I've heard in the evenings the Pit Bull owners come out and things get a little dangerous. Short of the city passing a no Pit Bulls in Dog Parks law there is not much that can be done.
I will go in the early morning but won't stay long. To see some good photos of this park check out http://www.dogparkriot.com