My son (11 1/2 years old) and I were out in Phoenix on his spring break for a few days and wanted something fun to do. Found this on groupon and I'm so glad we did it. Brandon is super laid-back, friendly, and knowledgeable.
The bikes are easy to use, fun to ride and quick to learn. If you can peddle, you're pretty much good to go. Part of the time is spent "commuting" to/from the desert area, as you meet in a peculiar 'commuter lot.' So, pay attention to the directions you're given after confirming the reservation.
We did the 8am tour on a Thursday with an older couple and it was super fun. Brandon shared quite a bit of info during the tour and made sure to communicate changes in terrain to everyone in the group. Very patient guy.
I want to do this again and I want to do a longer one next time. :)