Shelly, Not only is the dealers explanation absurd, it is totally disgusting. Having spent 23 years in automobile repair, I took pride in accurate diagnosis of service concerns. The explanation of Florida roads being hard andhot saddens me deeply. Excessive tire wear can be caused by a number of issues i.e. Over or Under inflation, Under inflation you get excessive wear on the edges of the tire tread, Over inflation you get excessive wear to the center of the tread. Excessive wear can also be caused by improper suspension alignment, and damaged or worn suspension components.
Shelly, I suggest that you take your vehicle to a reputable tire dealer, (preferably a tire dealer that represents the brand of tire on your vehicle), have them perform an accurate diagnosis to pin point the actual cause of your adverse wear. If the tires are defective the manufacturer may warrant them on a pro-rata basis. Good luck Shelly, I am going to follow this question with hopes of a satisfactory resolution.