Of course, this is not really a Portland-Dalles Loop—I start and end in Camas, you can figure out the alterations for your starting point.
This is probably described better as the Historic Columbia River Highway ride with the Washington side thrown in for good measure. It is probably one of the most documented popular rides around for good reason—scenery. I have done this in a number of incantations, including a day ride to The Bridge of the Gods and back (~90 miles).
I would recommend getting the latest map and description from the Oregon Department of Transportation. I have used their maps from the September 2004 brochure when building these pages. (I could not find a copyright so I guess that is ok.) This brochure has a number of good tips on what you can find in a town such as museums, etc. More maps can be found at various state sites and I have tried to link them from my bike home.
This specific ride was done on the weekend of September 29 and 30. The weather was a little dicey. Saturday was a grab bag of rain, sun and wind (head and tail) and Sunday was rain, save about two hours at the end of the ride. Therefore, the number of pictures on Sunday (rainday?) were very few. Additional pictures have been thrown in from other trips (noted) to give a good visual of the trip.
So we start at my home in Camas.
The Washington side has a number of trucks, since it is a state highway. Truckers not wanting to get a Oregon permit take this route. There is no escaping it. The Oregon side has a lot of bike paths, but it too puts you on the freeway and, at times, in not too pleasant a spot.