One of the top concerns among my non-monogamous clients is how to meet other open couples and singles. It can be tough to find community especially for people new to non-monogamy.
Here are a few of the groups my clients have said they enjoyed attending:
She Bop - She Bop is a woman-owned sex toy store and education center in Northeast Portland. They frequently offer an educational session for folks considering non-monogamy. I highly recommend attending one of their trainings for couples.
Portland Leather Alliance - is an organization based in leather appreciation and sex-positive community. They frequently host "munch" events for potential new members where you can meet others in the community. If leather or BDSM play is a potential interest for you I recommend attending a munch to find local community.
SPEEC- The Sex Positive Education and Event Center has recently opened in Portland, and while I haven't sent a client there yet, I am certain I will. This organization is lead by a number of sex-positive community members I have long respected professionally, I anticipate great things from them!
Portland Q Center - Occasionally the Q Center offers a poly support group and one for open relationships. They frequently offer them for partners of gender non-conforming folks (SOFFA), bisexual folks, and people who are just coming out LGBQ (as well as one for new kinksters). Check their calendar to see if there is a group for you.
Portland Poly MeetUps - There are a number of polyamory-focused meetup groups in the Portland, OR (and Vancouver, WA) area. Check these listings to see if there is an opportunity that speaks to you.
Sex-Positive Portland MeetUp - There are a number of sex-positive themed meet up groups in Portland and the surrounding area. Check here to see if one resonates with your needs.
Portland Polyamory Outreach Group - is a local organization dedicated to sharing resources for poly folks in Oregon. Check their site for groups, organizations, and meetups near you.
Best of luck to you in creating community. If you need help or support please let me know, I am happy to help.