I'm staying in the hotel zone and I'm looking for a nice restaurant where I can get good seafood; preferably tuna steak.
Not sure about tuna steak but Mocambo on the ocean near the Riu hotels or JC Capitan on the lagoon near the Westin are great for seafood. There is also another place a few steps from JC Capitan that sells some great seafood with seats overlooking the lagoon (don't know the name of it and its very rustic and simple place).
Ditto on Mocambo. been there three times and they have good fare at good prices. Also a very nice setting on the beach.
Mocambo and JC Capitans are moderately priced. Harry's is a joke. No bargains there. I am having lunch today in the barrio where a shrimp dinner costs $80 pesos, a michelada of 1 lt for $35 and you can get a whole fried fish for $140-$220 depending on the size. They bring them to the table and you pick your own. In the HZ the Mocambo buffet is a great deal, and right on the water with a great view. A nice new place by a long time company, called Habichuela Sunset, is at km 12 on the lagoon side. Menu varies but the atmosphere, view, service and quality are excellent. I would recommend trying this one. I have and it is wonderful. Oh, and Lorenzillo's, better known for their lobster, has excellent fish dishes as well. A tiny bit more $$ than Habichuela Sunset but worth the difference.