India has a large number of local languages and dialects spoken, of which Hindi is considered the most common language. Even though sections of the population use Hindi to converse on a daily basis, a working knowledge of English can be quite common. Most corporates and big businesses do not conduct any part of their work in Hindi. English can be thought of as a language that is spoken in most parts of the country, especially in the corporate world. It is not necessary to learn Hindi to survive in an Indian environment, but the option to learn that language is always open for the enthusiast.
If you ever need to converse in or translate Hindi to English or any other language, India has a thriving translation and interpretation industry for you to consider using. But since such situations would be more unlikely in a corporate setting, a good working knowledge of English is all you need to communicate with people in India. There are places in India, especially Southern India where although English is spoken, most people are not well versed in Hindi.
Depending on which state you find yourself living in, learning Hindi could also turn out to not help you at all. The multiple languages and dialects prevalent in India make it difficult to pick any one language that suits all purposes. But since corporates and businesses tend to want to expand outside the country, or expand inside the country – using English, a popular global language is the best way to ensure communication with people from many different parts of India.