Best to come between Spring and Fall on sunny days, if you use your school ID, the entrance is only $10/pp. We couldn't really see much things, other than the cactus as the temperature was really cold. I was going to come here for the Luminaria, but since the entrance is usually closed by 3pm, we couldn't make it on time cause we got to Phoenix around 4pm.
It's a good place to visit to learn about cactus or desert plants, very nice view of the hole in the rocks as well and in the summer I think there would be some butterflies around the garden.
I think this place is worth a visit if you're in town, otherwise, don't make a trip just for this, cause it's pretty small park.