Stop eating at those sanitized tourist taco places in hotel zone. Locals dont eat there for a reason - overpriced and bland.

Mercado 28 has incredible cochinita pibil for 25 pesos. The lady with the blue cart near the entrance makes the best sopa de lima ive ever had. No english menu but point and smile works fine.

Parque de las palapas at night has elote vendors and fruit stands. Get the mango with chile and lime for 20 pesos. Trust me on this one.

Honestly if you see other tourists eating somewhere its probably not authentic. Follow the construction workers and taxi drivers - they know where the good cheap food is