Check area blogs.  Talk to the craft store people, see if they have a bulletin board. Look around in hippie-type health food stores.

Though I use 'kokopellime" as my nom de plume on the forum (Kokopelli is the Hopi & other southwestern/Meso American native people's fertility deity, bringer of abundance, trickster and lothario, often portrayed playing a flute).  I happen to play the Native American flute (NAF) and he represents my creative spirit.

My actual name is Irv Sheffey and I live in southeast DC, the other end of the world ;-) from Takoma Park. I love your neck of the woods (including Takoma, DC) and I can come up your way, just let me know where we can meet for a coffee or tea that has nearby parking.

I came across reference to Pyramid in the hopes that they might have a PM class, but like you notice, they don't offer any at the moment.  Politics & Prose had a workshop earlier this year according to a Google search and I'm hoping they might sponsor another.  It seemed to be a Master Class of sorts, featuring an artist from France who apparently has an international following.

As I noted above that I play the NAF which is kinda off the beaten path of musical scene in DC, but we have a Potomac NAF Circle that meets monthly to show and tell newly acquired or treasured old flute, play (usually improv) and just enjoy what the flute brings together in terms of community.  Without getting too far ahead, having a similar circle for local PM enthusiasts, could help promote the craft beyond what most people know of it.  We'd do what the forum does but in-person.

Please send me an email at irv.sheffey@sierraclub.org so we can exchange numbers.