Best meal: Relleno negro at El Faisan y el Venado, in Playa del Carmen, on Hwy 307, east side, at juncture with Juarez. Excellent ink black turkey/chorizo)/hard boiled egg stew that tasted like the flavor (but not heat) of black peppers. Great menu of Yucatecan food.
Second best: El Meson del Marques in Valladolid. Pretty place, sweet staff. Longaniza de Valladolid were very good sausages. Sopa de lima was good, not great. Pok chuc was simple and good, a little dry. Excellent fruit at breakfast. (Good hotel overall).
Must to avoid in Merida: Amaro, calle 59 nr/60. Truly awful. Sopa de lima was inexplicable: greasy sauteed onions and peppers, floating in 2 inches of pure yellow oil. Beneath the oil there was a little broth and some chicken, but the thing was inedible even when the oil was poured off. Staff twiddled nearby while I waited for my meal (enchiladas verdes), which it turns out had been forgotten (there was only 1 other table occupied). When they finally made it, they were terrible: extremely watery, flavorless green sauce poured over lukewarm tortillas, and the whole thing doused in canned parmesan cheese.
Okay in Merida: Portico del Peregrino was okay. Good enough pollo pibil, but nothing was outstanding, so if something else sounds better, it probably is.
Lunch stop near Uxmal: pretty diverse and cheap food court in Ticul, near Uxmal. It's right off the highway through the center of town, hard to miss. Had a simple but tart escabeche de pavo, good soup. Costillas nearby looked awesome.
Pretty spot in Tulum: La Vita Bella, on the hotel/beach road a few hundred feet down from the ruins. Good, big, though a bit pricy, Italian pizzas on a gorgeous stretch of beach. Very mellow.