Your GMAT is solid & although your GPA is on the lower end you can use the optional essay to explain that it's because you had to work your way through school. I wouldn't worry too much about years of work experience. 3 years is solid & although an internship isn't seen as being quite as valuable as an actual job (since it's harder to really show impact) it's still worthwhile. Coming from S&P is totally fine assuming you have some strong recommenders who can speak to examples that show your business skills. I think Wharton & Booth are going to be a bit more in the reach category but they are within reach assuming strong essays and you have a shot at CBS for sure. One thing that does not come through here that you'll want to be sure to show in your essays is WHY these goals are your passion & the impact you plan to have in your career. Schools care not just what you plan to do but WHY and what exactly you hope to accomplish.