Yeah, that is a challenge that lots of different places have been trying to tackle in different ways, especially at a more local level. Examples of that are the NYCDH site, DH Philly, and Virgina DH Consortium. Those are basically attempts in other places to tackle the same problem, with varying degrees of success. Difficulty for all is finding the people who should join up in the first place, which is more at the heart of your question.
That said, I'm more confident about the regional efforts to build a DH community than I am with an effort at a national or international listing by location. I suspect that there will be more word-of-mouth growth at that local scale to build up membership in such sites (both NYCDH and VA are using Commons In A Box, I think, so setup is pretty easy).
If you're in the Santa Cruz neighborhood, I think some folks at UCSC have at least started talking about how to build up a group for that area.
I haven't been especially active on it, so I don't know how helpful it might be, but there's also the DH Slack, where you might be able to ask and spot people in your neighborhood.