Mahers are from Gujarat and hence speak and write gujarati, one of the hundrends of different languages spoken in India. Hindi being the official langaunge of India.
Gujarati is the official language of the state of Gujarat and is spoken by 70 percent of the State's population. Gujarati started out as an independent language around AD 1200. It is now one of the most developed languages in India.
The Mers have their own dialect of Gujarati that is related to the Kathiawari dialect.
There is a long list of books written on subject of Maher culture, many are written about the bravery of Mahers. Most widely read book is "Maher Jawan Mardo" by Bharat Bapodra.