Is "Tell Them Not to Kill Me!" written in prose?
Prose is writing that most closely mimics ordinary speech. It is not poetic in any sense—lacking "meter and rhyme," but uses the rhythms and patterns of everyday speech.
In Juan Rulfo's short story, "Tell Them Not to Kill Me!", the author uses prose.
"Tell Them Not to Kill Me!" is the story of a man (Juvencio) who is going to be executed for a murder he committed many years before. He is appealing to his son (Justino) to intercede on his behalf with the colonel who is planning to carry out the execution for the murder of Don Lupe.
There is no reprieve for Juvencio because Don Lupe was the father of the colonel. We learn that Juvencio's murder did not bring death to Don Lupe immediately, but that he suffered for days, even still worrying over his family's fate. The colonel at least shows Juvencio more mercy than Juvencio had shown Don Lupe by ordering the soldiers to allow Juvencio to get drunk so he does not feel the bullets so fully, therefore not suffering—as his own father had suffered.
The story is told with narrative text, mixed in with the dialogue that would most naturally have been used by the characters in the story. The story has been translated into English, but still copies the cadence and flow of "normal" speech patterns and a storyteller's narrative.