sparky, there's a detour route in place during the I-205 path closure for MAX construction:
http://trimet.org/i205/index.htm
the detour is not too swell; depending on where you're headed in Gladstone, you might continue on the Springwater west to Linwood, then south to Harmony/Lake/webster bike lanes on in to Gladstone.
you can check out this area on the Metro bike map:
http://bycycle.org/regions/portlandor
& click on "show bike map"