Yelp is the specific-for-food option. Everyone uses Yelp over here.
As a guide: Yelp is better for restaurants, bars, and clubs; Tripadvisor is better for hotels and touristy things.
Sorry, you guys are right... I didn't realize that Yelp is indeed what I'm looking for. Frankly I haven't started exploring the food places for our US trip yet, and so far, I saw the Yelp reviews for car rental and hotels (aside from Tripadvisor).
Now I've got the Yelp app installed!