Oh yeah - forgot to mention, I'm in Zone 5.

-Diggity

I'm in zone 5 with a slope in my backyard that has all the same lovely characteristics you list. Covering it is a variety of sedums and rug junipers. The trick was to plant them in pockets so they could catch and hold rain water.

Over the years, the lilacs and wisteria have become established and now part of the slope is shaded. Periwinkle and hosta grow on the shaded part.

Daylilies will work. And I have seen Stela D Oros pretty cheap. If I were you I would divide them so they are only one or two fans when you plant them they will fill in like crazy. Ornamental grasses usually like hot sun. Some varieties spread through runners and would fill the slope. Both daylilies and grasses can take poor soil.

There was an article in Backyard Living a couple months ago about a man who gardened on such a slope he tied a rope around his waist and secured himself to tree while doing so. What he created on this San Frasisco Hillside was quite incredible You might see if you can find the back issue at your local library. It was a good article. Made be stop whining about my little slopes.

Do you have a view of this slope from your house or is this projects strictly for erosion control?

Vinca minor is recommeded for erosion control on sunny slopes, although I think it is prettier in part shade, it will do the job you need.