Yes. You can sow them now.
No. They don't need cold stratification.

Fountain grass may come true from seed. Zebra Grass probably won't come true from seed.

Japanese Grass? Is that Japanese Silver Grass (Miscanthus), Japanese Blood Grass (Imperata) or Japanese Stint Grass (Microstegium)? The first and second probably won't come true from seed, and the third probably will, but it's a nasty invasive annual, and you wouldn't want to grow it.

Fountain Grass may, or may not be hardy in your zone.

Thanks Donn, That's great news. I was hoping I could sow them now, and didn't miss the deadline. As far as the variety of grasses, I am not sure. I recieved them in a trade last fall on the exchange forum. I have seen fountain grass growing here. I see it in the summer, see the winter show and then see it return each year, as long as there aren't a lot of species it should be hardy here. Thanks again for the input, I'm gonna get to sowin my seeds.

P.S. How soon should I expect them to germinate? And with ideal conditions (water,sun, fertilizer (later)) how much growth should I expect this season. Thanks again