Losing weight in 2 months?

okay so i really wanna lose weight before i go back to school again. im a girl,16,and im 5 6, and 150 pounds. :( , i also have really big legs, and i hate it. and if you have any excersise ideas that help slim down legs that would help a lot! okay so i was thinking of limiting my calorie intake to 1200-1500 a day, and going for an hour walk each day, and going on the elliptical every day for about 30 minutes. also doing crunches, squats, and lounges. if i do this for 2 and a half months how much weight do you think i could lose? if you have any other suggestions that would be greatly appreciated! and i do not have access to a gym, or any other excersise equipment other than the elliptical and like a pool lol, and i also am not able to go for runs because i have really bad knees, ( they dislocate and stuff) and its just to hard on them. so pleasee help me!