I haven't played it so I don't know how strong the language is. It's set in a prison so I'm sure it is somewhat mature. Maybe too much for children under 14. I would assume it is the same language levels as the movies or slightly worse.
Maybe someone who has played it can answer that question better.
The story takes place in prison, so naturally there's liberal use of profanity at times, and given that it's an M-rated FPS, there's considerable violence (shootings, stabbings, fist fighting, etc.) and some minimal blood. It's certainly not a hard M, but it's a solid M nonetheless, imho.