The Portland Marathon is well worth running, but it's important to know which way to look.
I will start with the good news -- the January 2011 issue of Runner's World is right to note that participants in the Portland Marathon can expect to get a view of Mt. Hood if they look to the right while crossing the St. John's Bridge. This google maps snippet shows the view in question, and being familiar with its size and shape, I can verify that the white triangular mass toward the center right of this image is Mt. Hood:
The bad news is that Mt. St. Helens is not to the right, but more to the left, as this image shows:
The white mass slightly above and to the left of the red-brick-colored structure is Mt. St. Helens, and frankly -- stand ready for more bad news -- the chances are slim that you'll get a clear enough day to see it from the bridge.
For all this, the larger point of the RW article is perfectly valid -- the St. Johns Bridge is the scenic highlight of the Portland Marathon, and passing over it a rare treat even for most locals. Along about mile 17, depending on the state of mind and body, a sign reading "unmuffled engine braking" (for example) can come across as surreal, macabre, minatory, evocative-- one way or another, interesting.
If you run the Portland Marathon next year, please obey Oregon's laws against unmuffled engine braking or prepare to pay.