I dunno. We didn't say anything specific...but of course summer time would be the best time for both of us because of school.
Good. That's the time to go. The rainy season ends in early May most years. So late May-June when the rhododendrons, azaleas and blackberries are out in full force is a great time to go.
As far as things to do, I can't offer much with regard to Portland, though Multonomah Falls in incredible and you should see it if you're down there. But from Seattle grab a ferry up to the San Juan Islands. Make a day trip up to Friday Harbor. From there you can hike up the mountain and look out over the islands and Puget Sound. Incredible views. That's where I proposed to my wife.
Of course, it's pretty touristy, but you have to go to Pike St. Market for the flying fish, the original Starbuck's coffee counter, great food, art, street musicians and people watching. While you're down there, you'll be near the Seattle Aquarium, which is a pretty good one. And you can usually catch some great live music at the clubs downtown afterwards.
If you're more into outdoorsy stuff, there's great hiking and biking trails either in the Cascades (a short trip to the East) or the Olympics (a short trip to the south and west). Kayaking on Lake Washington is fun. There's also great river and lake fishing.
That's just the beginning . . .