Do all Metro stations have escalators? I have parents that would like to visit the city but they don't do stairs well.
Yes and there are also elevators in every station. Sometimes they are broken, but that seems to be happening less often now.
For the most part they do in the tourist areas at least. Can't say for every stop.
You shouldn't have an issue. Every station has elevators in addition to the escalators. Both break occasionally, but the chances of both being out of service at the same time is low.
This site lists the current elevator and escalator outages: https:/…Elevator-Escalator-Service-Status.cfm
Keep in mind that many of the stations have multiple exits, and sometimes multiple escalators at each exit, so just because one escalator is out of service doesn't necessarily mean you need to avoid the station.