My family went on a Segway tour up at the JW Marriott Resort, off of Deer Valley out by the Desert Ridge Marketplace. The guys there were great . . . our guide was Aaron, and he was terrific. Very good at teaching us how to ride these exciting "vehicles" as well as showing us around as our guide. You wouldn't believe how much fun these things are. It's a bit of an odd sensation to ride them -- but just a few minutes into it, and you are ready to go! Basically, you lean forward to go and lean back to stop. Simple.
And if you stay on the trails or sidewalks, you'll be fine. We had a couple of spills in our group, but those were from people who were "hot dogging" around on the things.
Every now and then, Groupon or Living Social offer a great price on a Segway tour. Make sure you use the company that starts out at the JW Marriott resort -- it's a beautiful location, safe sidewalks and you take a nice break at a great coffee shop halfway into your tour.