People tend to check in during these times:
Buy artsy gifts for everyone during their annual holiday show/sale
MECA contains an ever changing body of work, both student and professional. Check out its lobby and adjacent galleries for provocation any day of the week.
This place is Hipster Central. Avoid if you don't wanna look at this eye sore for downtown Portland. Some of the art isn't that bad, though. But seriously, fuck anyone who goes to school here.
The MECA library is free to browse and has some fantastic books the Portland library does not.