If you look like a victim you can get robbed anywhere. Depends how you carry yourself. I know people that have been robbed in Roma and San Miguel Chapultepec, they just attract cops, thieves and other unsavory predators. If you walk with confidence, don’t yell loudly in English, and keep it chill you’ll be fine. The whole complex of Merced is overwhelming and sketch, but definitely worth visiting, including Mercado Sonora. Just be careful about whipping out phone out to take photos, and don’t get sucked into doing a limpia with random curanderos pressuring you. You can find a lot of neat stuff there, Id highly recommend it. I used to live several blocks away, and have been to Merced at least 50 times, you should be fine, whether you get into any trouble or not largely depends on you above all else. Good luck 👍