I'm in the same boat. They blasted away part of a mountain to build my neighborhood about 3 years ago, and the steep slope that everyone on my side of the street has is quite intimidating. I have to put on my baseball cleats just to walk to the top!! Anyway, the landscaping was pretty shoddy, and the soiil is very rocky. They planted some grass that was supposed to grow to a certain height and then stop (perhaps some variety of Buffalo grass?), but there were so many weeds that took root (we back up to a forest, more or less). I am south facing, and even with the slope, the ground gets long periods of direct sun. I've read that traditional groundcovers like spurge and ivy are more partial shade to full shade plants, so I'm kind of in the same boat as you. I'm tired of trying to take out the weeds that take hold every spring, although I am quite interested in the insect life that I find in there.

I've used a seed mix called "Fleur de Lawn".

It's a mix of lawn daisies, and dwarf grasses. In the summer it could be mowed maybe once a month. I've let it go all year in some places, without creating a wilderness.

Here is a link that might be useful: grass/wildflower mixes