Naresh
I have eaten there several times, and the food is very good - definitely a step up from most of the restaurants around. Chances are you will have to book, which in itself is unusual in Puerto Rico.
There is another restaurant next to it called La Paloma which is also very good.
Both restaurants are on the far side of the beach from the Marina Suites. Just walk past the actual marina on the main road and then take the promenade behind the beach which will lead you straight to Oscars. I estimate no more than 10 minutes walk.
Don't dismiss the restaurants that front onto the beach, they all serve up decent food. The Gran Canaria is always very popular, with a musician called Felipe playing every night (I think he may part own it). There is also a restaurant called La Bolera in the park near to the shopping centre.
I personally do not use any of the restaurants in the shopping centre. Nothing wrong with them, I just prefer the more laid back feel of the others near the beach.
John