I didn't end up getting a heater. I'm rolling the dice that the gas company won't mess up like two years ago. That time, demand outstripped the supply that they (a multi-state gas company) had allocated to Tucson, causing pressure to drop too low in the main gas lines, so they had to shut supply off - and then people couldn't have their gas turned on until a rep showed up to do it.
I did go fill up the gas tank in the car, bought some bottled water in case any main water lines burst, and I plan to fill at least one bathtub for some extra non-drinking water.