I shoot raw only. When you run into stuff like that, there isn't enough headroom to work with jpg's.

Wind in the Southwest can be your greatest enemy, putting very fine dust in the air and if the wind is right and agricultural burning is being done in Mexico, smoke. We went to The GC and Sedona in May. It was hazy. I used a circular polarizing filter. I helps some. A UV filter is no help. All modern lenses have coatings to block UV.
I ran the pics through LR5, increasing the contrast out of sight and also the clarity and added a graduated filter effect to it too. Not very satisfactory. But here they are.

I know nothing about iphoto, but is there something in its menus that maybe refers to preferences or something similar? That's where I would look.

Can't you just set CS6 as the external editor instead of Elements?

Incredible.