What is the best diet for getting a beach body in 4 months?

I'm going away with my boyfriend in 4 months time and would like a flat stomach and hot beach body. I go to the gym 2-3 times a week at the moment, doing cardio to lose weight but i need to make a food plan. I've looked at atkins but people have recommended the south beach diet. Does anyone have any suggestions or experiences to help me out?