I've never been to India. But from blogs I've seen and read, most of them say that you can generally get away with not wearing conservative clothes in big cities such as Delhi, Bombay, and Bangalore. The same is true for spots with hoards of tourists such as Goa, Kerala, and Agra. A lot of tourists can get away with wearing off shoulders or shorts. However, they advise to dress more conservatively when going to rural areas, especially to small villages or holy sites that don't see much tourists.