Upvote:2
Following up with my experience:
I did not get allocated (or see, even) any Uber or Cabify in my 4 night stay in Mendoza -- not at the airport, not in Mendoza city, not in the wineries area. A friend reported getting allocated once from in town.
In the end, I relied mainly on remises ordered via WhatsApp (e.g. Mendoza Remiss offers this).
Note well -- this was in mid-late December 2018.