I live in Miami but am going to the Bay Area for a week or two at the end of July (lived in Oakland, SF, and Redwood City from mid 2014-early 2018). I'd love to try it while I'm there. I'll send you an email :)
How difficult are they to use if your balance isn't necessarily optimal? I tried to ride a cruising board back in college and.. well, broke my wrist when I fell (shrug).
I have fine balance normally so I've always wanted to try a Boosted because it'd be handy when I go into our SF office or when I do stuff in San Jose.
I rode a skateboard (badly) when I was in middleschool so I'm not sure how hard it is for a completely new person. I'm not super athletic, but I find it pretty easy.
The trickiest part of skateboarding is foot breaking and pushing, with the boosted board you really don't have to do either so it's generally a lot easier. I'd guess given a couple hours and a week cruising around a bit you'd be comfortable going pretty fast.
I wear a helmet and sometimes wrist guards depending on how risky I'm feeling. If you're in town and want to try it let me know.
Pushing the board accounts for a lot of the opportunities to lose balance. I don't have much experience with a powered board but I think it would be easier for me to keep balance on it.
A scooter's handlebars help but not as much as a bicycle, and I think it lulls you into a false sense of security.
In my experience learning to ride a regular longboard takes about 10 hours of practice across 5+ sessions. Learning to ride a boosted board to the same level of competence is a half hour endeavor. Really, the hard part of skateboarding is pushing, not standing.