Welcome to ATP, hope we can help out. I lived in Utah for 21 years, so probably a similar climate to what you're dealing with. I do recall the west facing bed beside our house was always a tough one because the house shades the bed completely until mid-day then the sun hits it like a hammer at the hottest part of the day.
I'd suggest a little pergola made from posts and a lattice top to attach to the house and go over top of the walkway as well. It will not only give that bed a little bit of filtered shade through the early afternoon hot sun, it will help keep that side of your house cool until you can grow some trees up to do the job. Deciduous trees on the south and west sides = shade and cool in summer, and sun in the winter.
It would give you a lot wider range of plants to choose from, as they still would get sun later in the afternoon, but not have to withstand the sudden onslaught. You could also grow some really gorgeous vines on the pergola like Clematis and (hate to admit it but I'm a fan of annual Morning Glories. They both grow pretty fast and the Clematis will repeat bloom while the MG's will bloom non-stop through the summer.
We eventually covered that whole west wall on our Salt Lake house with a Concord grape vine that gave us beautiful foliage and tons of delicious grapes for juice as well as shade for the house through the hot months. But the one good perennial we had going for years in that bed was
Jupiter's Beard (Centranthus ruber)
