1. Some varieties have sharp blades and can give you the equivalent of paper cuts. Some have stiff and very sharply pointed blades. Others won't hurt you in any way.

2. They won't attract any more snakes than any other thick cover plants. I'm a zone warmer than you, and right on the coast. I've never seen a snake in my grass.

3. Growth rate varies from one version of ornamental grass to another. Some are quite slow and others are quite fast. In general, a grass follows the old perennial rule; first year they sleep, second year they creep and third year they leap. A lot depends on how big the grass is when you plant it. I grow them from seed, and grasses which eventually grow to 6'+ will only be a foot tall in the the first year.

Something to keep in mind. Ornamental grass will only provide screening for less than half the year. Most of the taller ones need to be cut to the ground in early spring every year, and require at least a few months to get back to full height.

Here no one cuts there pampass grass down. I've only seen that done once becuase they were moving the clump. It get 10-12ft at the top of plums and makes a good privacy "fence" does take up some room though. The colered ones to me seem brighter if they get a little afternoon shade.

Amazon..chances are, the 10-12' grasses in your zone aren't Pampas Grass (Cortaderia selloana). The tall versions of it aren't hardy to zone 6. They barely get through the winter here in zone 7, and look so ratty they have to be cut back.

donn answered your questions pretty well already, but here's my take on grasses as privacy fences...

Whenever I hear someone who has not grown grasses want grasses for 'privacy', I get concerned they will be dissappointed. While there are many grasses that can offer screening, as donn pointed out, most will have a varied look throughout the year. Foliage in spring, blooms to follow, fall/winter appearance, cut back in late winter/early spring. They will not offer a fixed privacy height through the seasons.

Amazon, i also agree that what you describe is probably not pampas. cortaderia selloanna, unless you are a bit more coastal and possibly zone 7.

I also really dislike pampas as a screen. It makes a better specimen and when crowded has a bad look to it...IMHO.