I like your city, I live in Phoenix Arizona. I been to Lake Havasue many times for spring break, lots of fun. As a student I have study the flora of the Sonoran desert, your desert terrian is all right but is not realalistic. The mountains should be basin and range with broad falt valley made up of bajadas or piedmonts with flora arranged according to soil texture. Near the moutains the soil texture in course and shallow with palo vede( Parkensonia microphylla, cactus spp. ( Cylindropuntia, Ferrocactus, and shrubs Lycium, . Near the valley floor the soil texture is fine made up of clays and slits, only ambrosia dumosa, Larrea tridenata, and Atraplex spp., with very card pterocalic layers make building houses hard too. You should read a book on the natural history of the Sororan Desert if you fully want to sim a North American Desert city. Also to sim a desert having brown or tan color soil and a few cactus wont cut it. Aso a Plant Biologist and a person who plays sim city the simple desert system is a insult to the true diversity of the Sonoran Desert and the Cities that grace their presence upon their surface.
Other than that and for sim city you did a great job, sim city was never big on ecological soundness rather just pretty trees.
Darin.