Some of the lavanderia's are still used, typically by "more mature" ladies of the surrounding village or hamlet who do not have washing machines. Back in the day, it was the local gathering spot. I suppose the men repaired to their 'local' and the women to the washing spot. I am not being judgmental, just historical.
You can usually tell the still-operating lavanderias by the overall condition, whether the paint / plaster is reasonably fresh, and whether the place is overgrown by weeds. I would NEVER drink this water, as it is typically, but not always surface water. But, I have used it for soaking my Buff, sun hat, and feet from time-to-time.
When I walked from Lisbon this April- May, I saw quite a few that were clearly in good repair and likely still being used.
I hope this helps.