Where do local users of ALMA live and work?
No one travels to ALMA to observe; the observations are all carried out by staff working at the Operations Support Facility. (This is at an altitude of 2900 meters; the actual telescopes are 28 km away at the Array Operations Site, which is at an altitude of 5000 meters and is not permanently staffed.) Any "unusual/non-standard observations" would have to be specified in advance and encoded into the Scheduling Blocks (prepared files specifying the observations you want).

https://almascience.nrao.edu/about-alma/alma-site

I believe the staff at the Operations Support Facility stays in the Residencia. (More pictures here and here; pictures of the OSF, including the telescope control room, can be found here.) 

(I wonder if some future movie will film scenes there, as the James Bond movie Quantum of Solace did at the Paranal Observatory's Residencia in 2008...)

Visitors (who cannot stay overnight) are permitted on Saturdays and Sundays, though you have reserve your visit in advance.