We rode in the morning on the Martin Luther King Holiday. So (a) there was almost no traffic or people except in special spots, and (b) my wife and I were the sole customers, so it was like a private tour. We had a great time. Tucson is extremely bike-friendly (flat, lots of special lanes and paths), and on a tour of just about 90 minutes we saw several different neighborhoods and had two stops. One to go into the lobby of the historic downtown hotel (host to, among others, John Dillinger) and another to use the bathroom and eat a pastry (paid for by our guide) at a fun food court. We might have stepped inside the cathedral, but it was holding a big service for the holiday.
We saw old residential, new residential, historic fort and courthouse, new convention and arts center, the river, a tiny portion of the 55-mile bike loop, and several other sites. Our guide was well-informed and had a notebook of historic and other photos that he showed in conjunction with the sites we viewed. The bikes were one-speeds with pedal brakes and highly adjustable, so the ride was easy and comfortable, with lots of short stops for sites and the two longer stops for breaks. The guide also supplied cold water in a fit-on-the-bike bottle and the bikes had small pouches on the front handlebars for cellphones, wallets, purses, etc. The tour even had gloves for the (for Tucson) "colder" weather (it was about 50F in January).
All in all, a great way for us to be introduced to central Tucson.