As a person who spends a lot of time in the Columbia Gorge, I'd recommend it, especially if you're already spending time at the coast. There are all the waterfalls along the scenic highway that everyone and his mother has snapped from the road (some people don't even stop the car, but shoot through the [sometimes closed] car window). To really see the gorge, you do need to do a bit of hiking, assuming you are able. If you want to email me, brodyeratgmaildotcom, I'd be happy to make some specific recommendations if I know something about your fitness, your level of photo expertise, your gear, (are you taking an 8x10 or a small digital), and what you like to photograph. Arguably the gorge is best in the fall and winter when the waterfalls are full but it's lovely any time of the year, and considerably warmer in the summer.
Having spent a lot of time at the coast as well, I also think the mid and south coasts are better for scenic-landscape photography, especially from Yachats down to Bandon.
Good luck.
Eric