The official language in Mumbai is Marathi. However, because Mumbai is a cosmopolitan city (meaning it includes people from many diverse areas and countries) most people are able to comprehend English, and Hindi is also common.
Rupees are the currency used in India. One very nice thing about living in India for one year is that everything is priced in rupees. One U.S. dollar is the equivalent of 71 rupees. Therefore, prices relative to what we find in the U.S. tend to be cheaper here.
A bottle of water costs on average about 30 to 50 rupees.
My best meal this week was at the St. Regis Hotel, a full-on buffet that included a mix of seafood, South Indian cuisine, and more traditional Western brunch dishes. Mumbai is well-known for its strong dining options and because I was only there for three days, I did not get to explore this aspect of the city as thoroughly as I would like.