How often do they move most/all of ALMA's dishes?
The list of array configurations is given in the Proposers Guide and ten configurations have been defined for the 43 12-meter antennas. They have the form C43-x where x goes from 1 (most compact; 15-161 meter separation) to 10 (least compact; 244-16200 meter separation). The changes between configurations are shown in the Configuration Schedule; over the ~12 months of Cycle 6, it looks like they change configuration 14 times. There is a month long "Antennae Relocation Shutdown" in May 2019 as they transition from fairly compact to least compact - presumably because it takes a longer time to move the 43 dishes out multiple kilometers

As an example, here is a snapshot of the planned schedule for a year starting 01-Oct-2018 as it stands now: