Jim W.
Yelp
This place is located about 45 - 60 minutes east of Phoenix. It is just off Highway 60. We arrive just after they opened at 10 a.m. on a Monday (holiday). Perhaps due to the holiday, it seemed more crowded than I'd have expected, but the crowd was not overwhelming.
My wife had purchased some American Horticultural pass before the trip that got us in for free here (on the assumption that we can use it elsewhere later in the year). There were some shaded areas and plenty of sunny ones, so if you visit in the warmer months, bring sufficient water, a hat, and sunscreen.
When we first started out, a couple of the volunteers / docents engaged us in two separate incidents for several minutes of interesting conversation / explanations. Our only worry was that if they kept popping up at that pace, we'd never complete the loop. The density of volunteers thinned out quickly, though. They did provide some good background, though.
The layout is mostly around a large loop trail that circles behind a rocky hill and then returns along Queen Creek. It took us almost 2 hours to complete the loop, but we could have stayed in some areas longer.
They had areas dedicated to regions (such as Australia) and sections given over to particular species or sub-species of plants (cactus, eucalyptus, etc.). The signs were informative.
At one point you pass near a house on a clifftop that was built by the guy who founded the arboretum in the 1920s (Boyce Thompson). It is not open to tours, but was interesting to view even from a distance.
There was an alternate route on one side across Queen Creek that was billed as the 'high trail' or something similar. We didn't have time to explore it but it looked interesting.
They appeared to have some sort of food vending on the weekends, but as we visited on Monday we had to venture a couple of miles further into Superior for lunch afterwards.
If you have much interest in plants generally or just want to have a couple of hours relaxing on a nature walk, this is a great venue.