Phoenix? Really?
One of the most imporant things to me that makes a city easy to bike in is how close things are relative to each other (how compact the city is). The more compact the city, the more effecient the bicycle as a means of transport. It would seem to me that Phoenix is severely lacking in this area.
The biggest concern for me is the drivers. Friendly alert drivers who know to look for cyclists is what really makes it or breaks it.