A great place, no doubt, but with admission at $18 per adult, it has the feel of an expensive tourist trap. Why pay so much for someone to "show you nature"?
My suggestion: Go out and explore the desert on your own.
-Hike in the Phoenix Mountains Preserve area. (One of many parks.)
-Explore the saguaros and lush desert outside the city. (My favorite region is toward Florence Junction & Superior along US Highway 60.)
-Visit a retail cactus farm. (There are many!)
Then again, if you're a tourist and don't mind spending the money, go for it.