You might post on the Pacific Northwest Forum (I *think* that's the name), & also check around your neighborhood & ask people what they use, call your county agricultural extension office, check with area garden clubs, etc.

There's a very hardy and vigorous rose named 'Nozomi' - single flower, pink/white - that has a hardiness range from 5-9. It might be suitable for what you're trying to do on that bank.

If you just want to cover the wall and are not too bothered about flowers your best option is....ivy. There are some very nice variegated forms available which do actually flower. Another option would be Virginia creeper (Parthenocissus) the leaves turn brilliant red in the fall. It doesn't just grow in Virginia.....;-)