I've never been to Tucson, but I've heard that it's a bit hillier than other parts of AZ.

RGNY, you obviously have an abundance of cycling experience, so there are aspects of riding that you don't even think about when out negotiating traffic. It's another thing entirely for someone who is inexperienced in traffic to then also be thinking about how to become one with a fixed gear bike. Most inexperienced riders will encounter a situation that is unfamiliar to them and generally the first instinct is to coast, interpret what's happening, and then do what needs to be done. True fixies as you know don't coast so well. It's a potential recipe for disaster. At the very least, someone who is new to riding, or just getting back into it should opt for a flip/flop hub so they can ride SS until they are very comfortable with their bike, at which point they can flip the wheel around and go fixie.