Also being in the western Washington/Oregon area, I've grown both peppers and tomatoes with great success, so it apparently depends on the specific location (soil as well as area) and choice of varieties. My tomatoes are mostly heirloom and have been literally dozens of varieties.
O.P. didn't say what part of western Washington, but if anywhere near Vancouver/Portland, visit the garden show at Clark County Fairgrounds at the end of April and definitely visit Millennium Farms. M.F. uses no chemicals and has many dozens of varieties of heirloom veggies; their green house is fantastic for a gardener, better than a candy store for kids.
Of the veggies in my photo they posted on their home page, all peppers and tomatoes were purchased at their greenhouse (potatoes from Hints of Garlic in Ellensburg,). The photo was taken in July of that year (2000) so lots of growing season left. I'd say that photo speaks for itself as to whether we can get good production. The garden that year was about 15 by 15 feet. FYI, the green tomatoes there are ripe, Green Zebra.
My 2002 garden, as of the end of July, is posted at: http://www.pacifier.com/~glenna/ Pictures of several varieties (though only a few of what I've grown) of tomato are at the bottom of the page. These just happen to be the ones I photographed; they are all delicious. Click on the images to see a larger image. In each case, the slices are from the tomato they accompany (PhotoShop!). The descriptions are from M.F.'s product sheet.
I absolutely love that place and feel fortunate to have stumbled upon them at my first garden show in 2000 as I was preparing to plant my first real garden. The first year I purchased all plants (tomatoes, peppers, herbs, etc.) from then; since then, I've branched out but they are still my primary source. They are located in Ridgefield and several long-time customers drive from Salem (85 miles) to purchase from them; I like tomatoes but am not sure I'd drive that far for plants! <g>
For the beginning gardener in competition with the "old folks", those photos should show what you can learn in only two years (and digesting info from the experienced). However, I do not take credit for the garden . . . it grows in spite of me, not because of me. The "because of" is good soil, manure, lots of water, mulch , etc., not a mere human. (Just plain dumb luck probably figures into it as well.)
I second all that except the onions, though I know others who have had great onions, that has not been one of my successes.
Manure, definitely, absolutely (horse being best). I mulch well with grass clippings as I plant the seedlings and water regularly, for several hours once a week with a soaker system, twice a week in hot weather. We have good drainage in our location, the clay is 2-3 feet below the surface, luckily.
My experience has been that the proper watering has been the most important care, even more than direct sun. Most of my garden is in partial tree shade much of the day but thrives. Do note there is a difference between partial tree shade and being on the border of evergreens, evergreens produce denser shade and have other issues as well.
Just another viewpoint for western Washington/Oregon. As always, YMMV.