What language do they speak in borneo?
In the Indonesian part of Borneo they speak Indonesian and various Dayak dialects. In the northern part of Borneo, like Sarawak, they speak English, Malaysian, Hokienese, Hakka, Mandarin, Teochew, Cantonese, Murut, Melanau, Iban, Bidayuh, Kadasan, etc. But because their nationality is Malaysian, so they speak Malaysian Language, they call Bahasa Kebangsaan as their official language, while those who live in the Indonesian part of Borneo called Kalimantan, they speak Indonesian Language. I can and have spoken with them in several languages like: English, Malaysian, Indonesian, Mandarin, Cantonese, Iban and Bidayeuh, when I worked there as teacher/lecturer. The capital of Sarawak is Kuching, and most of the people in that city can speak at least in three languages: English, Malaysian and Hokienese. Some can even speak in Mandarin and Iban.
The Indonesian part of the island Borneo is named Kalimantan. The people living there are Ngaju Dayak, Maanyan, Lawangan, Banjar, Iban, Punan, and Banuaq). Besides these original inhabitants, you find Javaneese, Madurese and Chinese. Banjar is the moste widely spoken local language here, by at least 5.000.000 people. As it is part of Indonesia, the official language in Kalimantan is Bahasa Indonesia (Indonesian). But for the majority of Dayak people, this is only their second language. As for the Malaysian part, the poster above seems accurate.
I agree with you, they speak Indonesian and various Dayak dialects. I learned this at college, by the way is there is any fellow college student here, I’d recommend you to check this website here, it has good deals and discounts that maybe useful for you, because I know we all want to save money to keep studying!