Other favorites: La Lomita,-edge of town Bruja's-in the colonias, Lo-lo Lorenas- wonderful! must make reservations. Lo-Lo is presently off island..don't know if she will be back in time for your trip.
I've know Lolo for ages and she is an incredible cook (and quite a character !). She used to have an awesome restaurant downtown (and several other smaller joints depending upon her mood…
. Nowadays, she owns a guest-house/bakery in La Gloria colonia (near the Superior and Coca Cola warehouses). The croissants she bakes are heavenly (better than most I have here in Paris) and she also makes set-menu dinners by reservation only in her cute little yard. Not Mexican food, but probably the best meal you'll have on the island. She should be back on the island mid-september, don't know when she'll be open for business.
Back to Mexican food :
Downtown, there's a place on Juarez, on a corner across from a lavanderia, that serves good inexpensive Mexican food. Sorry, I can't remember the name or exact location. If they're full, they'll send you to a small taco place just up the street. Same owner and equally good.
It's been ages since I've been to La Lomita, but really liked the place. The Poc Na hostel also serves inexpensive dishes and it's a fun place to meet (young) people if traveling on your own.
On Sundays, several places in the colonia serve Cochinita pibil, typical pork dish from the Yucatan, the sauce/marinade is somewhat similar to that of Tikinxic fish (which you can have at Playa Lancheros).
For fish and seafood, plenty of options on the waterfront north of the ferry pier.
I also like Café Mogagua for the friendly service / lounge ambiance (food and cocktails are good too) and heard great things about the chicken wings from Bobo's fish&chips (haven't tried it myself yet).
Enjoy Isla !