I wish I had such small problems to deal with. Just open a couple up so the salad is pulled out a little for your display. Fogging over is good it shows that the mixture is fresh & cool. (You could cool the outside air to the lettuce temp or vice versa!)
Describe your product very well, such exactly what greens are included in your bag and after showing your sample bag they will buy those fogged up bags lickitty-split.
Make a big wooden salad bowl display with pictures of salad stuff on front put your bags of salad in this! you will sell out in a very short time.
check out picture link.

Here is a link that might be useful: {{gwi:1041906}}

I don't pre-bag my greens, I sell by poundage or my bag.

I don't worry about foggy bags, it does not seem to hurt sales at all. That said, I never put more than 3 bags of any one type of greens out on the table. The rest stay in their coolers until I need to restock the table. Shade also helps a lot. If I'm selling at a morning market I will put a banner up on the east side of the EZUp, if it is an evening Market than it goes on the west side.

By Banner I mean pre-made banners that say things like Strawberries, Locally grown, etc.. This is excellent advertising as well as shade.

If you have a shelter with sides these also work well for shade, though they also block the public's view of your stall unless they are in front of it.