This is an old article from 2016, seems like the F-5s are still hanging on, quoting Wikipedia: "Due to high operating costs, lack of parts, and the extreme age

This is an old article from 2016, seems like the F-5s are still hanging on, quoting Wikipedia: "Due to high operating costs, lack of parts, and the extreme age of the aircraft, the Mexican Air Force retired all but 3 F-5s in late 2017.[16] In early 2019, the Mexican Air Force received repaired engines for their F-5 fighters, as part of an effort to return a handful of the aircraft to operational status.[17] In early 2023, restoration work on F5 airframes has begun with the intention to have a total of at least 9 F5s in active service." It might not be a state of the art fighter, but the F-5 is a very good looking plane.