Hey Lyn, It does sound like your climate is somewhat similar to mine. We're on the east side of the Cascades at about 1600 feet so it's zone 5 here compared to your zone 8. Much colder winters for us, but we do get the heat in the summer.
I grow a little bit of everything here with varying degrees of success. I do love peonies, with their gorgeous blooms and lovely fall color. I let them flop for the winter which gives them a bit of extra mulch. I've never seen a dogwood tree around here - must be too cold for those. I seem to do really well with artemesias - they seem to like our alkaline soil and it seems to me like you can cut them back any time they start looking ratty. Powis Castle is one of my favorites and I like the silver foliage that many of the artemesias have.
I don't do a major fall clean up, but instead run our lawnmower over the millions of cottonwood leaves and pile them in my flower beds for the winter. We frequently get really cold weather prior to getting a decent snow cover, and the extra mulch helps.
Other plants that do well here are daylilies, irises, spirea, some of the hardier hydrangeas, mountain bluet, russian sage, smokebush, sumac, clematis, veronica, various grasses and scads of other things. These are the ones that popped into my head as being easy keepers. We're blessed with an abundance of water here for irrigation, and so can grow things that some of our neighbors up higher on the hills cannot. We are also in wildfire country so it's important to keep a green zone around our house.
I live in a small town also with limited varieties of plants for sale locally. I either trek to a larger city or go over to the coast where they have nurseries to die for, although I do have to be very careful and read the tags for zone information when I'm on the other side of the mountains. Even the larger town 90 miles away sells a lot of stuff that won't grow here.
I've never been too much of a planner - more of a plunker so my gardens aren't really something from a magazine. I just move stuff if it doesn't work out. I've planted a number of trees over the years as well, which gives us more shade and changes things up a bit as they grow.
Best of luck with your evolving garden!
