I know Wikipedians meet up regularly, but what about the Esperanto Wikipedians?
Yes, there are many Esperanto Wikipedia meetups. Those are usually organized as a part of Esperanto congresses, or sometimes, as a part of Wikimanias (e.g. https://wikimania2016.wikimedia.org/wiki/Meetups/Esperanto). Once there was Esperanto Wikimania in 2011 with 80 participants(https://eo.wikipedia.org/wiki/Esperanta_Vikimanio)