i think Ron's got it sussed - I'd go I-205 path to Springwater to Gresham-Fairview trail to Halsey bike lanes to Troutdale. I'm sure you've got a good bright front light or 2, because it's dark out on the trails!
Here's the Gresham bike map link in case you need it:
http://greshamoregon.gov/live/gettin...e.aspx?id=3118