I contacted the Tucson and Arizona Velodrome Associations the other day, haven't heard a response. I hope they still exist...
Their goal is to establish a velodrome in Tucson, they also organize(d) fixed-gear rides. They would drive out to San Diego for the velodrome there. I don't know if the drive is worth it to me on a regular basis when I have such great terrain around my house, it would definitely be worth at least one visit when I'm in San Diego the next time!