Both Seattle and Vancouver great urban hiking-lots of great neighborhoods to explore by foot. IN Vancouver, walk around downtown, to Granville Island (or take the little ferry) to check out the farmers market, and then look at walking to Kitsilano on west 4th where there are lovely shops and restaurants. I also love Stanley Park which covers a large tract for a city park with great trails and options to hike.
In Seattle, get ready for some hills! Capitol Hill area is great to explore, and all along the waterfront whether it be Puget Sound side or along Lake Union/Lake Washington offers some great walking options right out of your hotel lobby doors. On the North side, Gas Works Park is fun to explore on foot (or rent a bike), Wallingford has sole proprietor shops/restaurants and the University District too. (See similar Seattle area questions where there's info on bike trails to try). Discovery Park is one further north in Seattle (check out the washington trail association website for ideas in and around seattle for hiking) I've hiked around Mt Snoqualmie and it's gorgeous.
Last suggestion is to take a ferry to Port Townsend, and even consider staying a night there if it times well with a music festival, country fair or other cool events (http://www.ptguide.com/) that may be happening there. Port Townsend is a lovely spot, with great character, views of the sound and local walks. almost 8 years ago
The Moore is a relatively inexpensive but clean and central hotel in Seattle. Other Seattle tips at http://traveleater.wordpress.com/seattle-field-notes/. Vancouver tips at http://traveleater.wordpress.com/vancouver-field-notes/
Both cities great for walking around and sampling the food. In Vancouver you can go whale watching off Granville Island - guaranteed sightings in summer or they'll take you out again for free. In Kitsalano, youn an swim in a giant salt water pool near the beach. Hiking on Stanley Park and up on Grouse Mountain good. Take a trip to the Capilano Suspension Bridge. Or even go up to Whistler for the day. Have fun! almost 8 years ago