For what it's worth, mites aren't generally as much of a problem in areas with high humidity, and the Seattle area has some good moisture. I'm not saying that you'll never have to worry about mites, but I don't think that they should be your first concern.
I've had a very high rate of success with the Bayer, but obviously experiences will vary. I had a mealy bug breakout about a year ago... sprayed all of my plants once (a good drenching that got to the roots) and never saw another one. I did follow up about a month later with a second application anyway, though. I've never had any scale, though...
- Matt