Be wary of strikes, or bandhs, called by political parties. Check the newspaper, and if you notice that all commerce seems to have come to a halt and businesses all seem to be shuttered, stay at home.
talk
The principal language spoken is Marathi. Hindi and English are widely spoken and understood. Mumbai is fairly cosmoplitan, with many languages, including English being spoken. Konkani is a minority language closely related to Marathi, spoken by the eponymous Konkani community. Though Konkanis are common in the Konkan region, they are a minority everywhere.