The hotel looks out on the Willamette River, which runs through downtown Portland. Waterfront park is direclty in front of the hotel on the west side of the river. Across the river there is a new walking path called the east side esplanade. You can do a nice loop walk by heading north from the hotel to the Hawthorne bridge (the first bridge), crossing it, walking north on the east side esplanade until it ends at the Steel bridge, and then returning on the west side. (You can do the loop in either direction.)
If you want to rent a bicycle there is a bike rental business in the River Place walk, across the street and to the south by the river.
If you want to explore in another direction you can look for the fountains used for the proceedings covers. You can walk west on Clay from the hotel to 3rd Ave. where you will find the Keller fountain (between 3rd and 4th, and Clay and Market). The Keller Fountain is featured on the Haskell workshop proceedings. From there proceed south on 3rd Ave until it becomes a pedestrian way. Follow this path to Pettygrove park, where you can see a statue titled "The Dreamer." This statue is used for both the Erlang and ML proceedings. Continue south and you will come to the Lovejoy Fountain, which is on the ICFP proceedings. The PSU Computer Science department is located in the building between the fountain and 4th Avenue.
Also good for walking: The Park blocks: the blocks between 8th and 9th Avenues constitute an almost continuous string of parks through downtown.
Classical Chinese Garden
The Oregon Coast (recommend Cape Lookout)
The Columbia River Gorge