One of my favorite "deals" is the fish and chips at Britannia...It's huge and delicious and pretty reasonable. They also have a different plate for 99 pesos every day at happy hour (burger and fries, chicken wings, etc), and usually a good "daily dinner special" for around 200-250 pesos.
Britannia Bar Sosua - Home
For cheap, delicious chicken, my favorite is the "Simong" stand across from Dominos/Four Roses. For more than three years. I was super loyal to Pollo Nortena, just past Club Residencial, but after trying Simong's chicken, I haven't been back. A half chicken with tostones is 125 pesos.