I go there because the owner carries really nice quality plants, and is very knowledgeable. Doesn't mean I haven't murdered a few of his plants, though.
I think they get a lot of their plants from Monrovia Growers, which is one of the wholesalers on the West Coast.
We don't get much humidity. The Butterfly Bush is planted in full sun (and it hit 106* a few times this summer) and seems to be thriving, but it does want regular water. I have that whole bed on drip, which I run every third day, but during heavy heat I will check it daily, and give it a drink.
I have azaleas and rhododendrons, too, but the rhodies only get partial sun and the azaleas are planted in the shade of some Japanese wisteria, so they only get filtered sun.
I know I've mentioned it before, but I just can't believe how incredibly beautiful your side of the country can be.