Hi Kimberly,
I'm glad your question showed me a new way of pop-up coworking, via Alex's lnk to the SF makerspace. Where I live, north of Austin, there used to be a jelly but it disbanded and we don't have a cowork space (yet.. someone is working on theirs sooner than mine) We don't have a good space either AND I've tried coworking from a makerspace, too (TechShop) with no luck. I've had good success (if you call 8 ppl per cowork morning) at two local coffee shops. Monday in one city, 9-12noon and Wednesday in another city, 9-12 noon. Regularly scheduled with a growing regular cast of characters. I'm considering 'renting' a table (to ensure we have space together) soon with one location. Another location tends to be busy, but I want to host at least 1x month there, but they're not into renting a table (even if no one comes but me.. work on that one).
It's really helped me get the word out and build a community. This community has been aided by posting the events on local FB community pages (at least for my area).
Good luck!