Sounds to me like the damage you refer to is actual from too much CH, thanks to the hard water in AZ. You are talking about white scaling all over the pool, right?
Generally speaking, the salt levels needed for a SWG to work are not enough to damage anything. Even when people talk about an SWG ruining their coping, it's usually because they had very low quality coping to begin with. The ocean, which rusts everything and ruins stuff because of salt, has a concentration around 35,000 ppm or greater, pools typically have 3,500 or less ppm. Even pools dosed with bleach have salt in them, typically around 1000 ppm or more.
Anyway, a properly balanced TFP salt water pool will not damage your pool, assuming the builders used decent materials. Also, over time, you will save a considerable amount of money with a SWG since you pay for the hardware and salt up front, and then nothing but electricity for years (5-7+ depending on how oversized your SWG is), and just have to replace the cell when it wears out years down the line. All the bleach you add every day does begin to add up.
