Rhinelander in Portland/German in the Pac NW?
The Rhinelander is a classic. Gustav's (next door) also serves good german food in a more informal setting. The Berlin Inn rocks too!
There's also a german deli that has serves a great lunch somewhere in Beaverton. (There's also a Gustav's in Beaverton). I'm sorry I don't remember the name, but it's somewhere near the Beaverton / Tigard border near 217. If you're on the west side, this may be more convenient. If you're on the east side, just stick with 12th and Powell.
The Rhinelander is a long-time Portland institution. It was for many years owned by Horst Mager (is it still?), a well-known Portland chef. Mager also helped start the Western Culinary Institute in Portland --now a Cordon Bleu cooking school. Food is authentic, and good to very good, though it falls short of superlative. The place is a bit "touristy": roving accordion player in Lederhosen, waitresses in Dirndls, you get the picture. Gustav's Bier Stube is the beer-hall annex of the Rhinelander. Great for Oktoberfest.
Allow me to suggest The Berlin Inn for something more akin to what you might actually find in Germany. It's at SE 12th and Powell Blvd., just south of Powell. Schnitzel are wonderful, wurst are very good, but the rouladen are my favorite. Absolutely do not, under any circumstances, miss Marianne's house-made deserts.
3131 SE 12th
The Berlin Inn has the additional advantage of being right next door to the Edelweiss Deli, a very good German deli, with very limited hours. Try them Saturday mornings.