Window tint is your best defense against heat. Its help protect the interior, keep things cooler, and shade blinding headlights at night. Not mention it makes any vehicle look much better and personalized. I order pre-cuts on ebay for $25, normally 200-400 for a professional job. Running the A/C creates more drag, thus the motor has to work harder and will lower the MPGs on any vehicle. Any turbo charged vehicle will also be negatively impacted by hot weather. I experience all of this in my gen 1 as well.
Tinted windows also help the A/C run more efficiently, because less heat inside from the windows means less actual "run time" for the compressor, which means less drag for a vehicle already running the A/C. The down side to window tint IS night driving, and if you're like my wife, she doesn't like the dark tinted windows. Because of that fact, with my most recent vehicle purchase, I went with Mesa brand window tint, and I believe it's "Mesa 5" tint, which is virtually colorless ... and it's quite pricey, but WOW does it block heat! I'm amazed and wish I could install it on the windshield because it's so awesome at blocking heat and I think it was money well spent.
Your vehicle should see some mpg improvement as it breaks in ... and as a prior Eco owner, myself and others can attest to the fact that you might see slowly steady increases in mileage until you get 10 to 15 thousand miles on that engine. Driving style and fuel octane also make a noticeable impact on mpg.
