I haven't biked much in Portland, but I'll give a thumbs up to visiting Seattle in summer! (Keep in mind that our summer doesn't tend to start until July 5th... Pretty much a law here that it has to rain for the fireworks on the 4th, then turn sunny and dry for the next two months straight.) There's a really great variety of bicycling here. There are some fun urban routes--even some relatively flat one--easy ferries to scenic and challenging riding on Vashon and Bainbridge islands, and good mountain routes not too long of a drive away. It's also just a good way to get around the city.

If you end up visiting Seattle, feel free to drop me a line if you have questions or want suggestions