Nick and Priyanka were decked out in traditional Indian suits in her hometown of Mumbai Wednesday as they kicked off pre-wedding festivities. Priyanka wore an embroidered pastel blue suit and Nick sported a pink kurta.

They were outside Priyanka's parents' house as they headed to a puja -- think prayer service.

The couple's reportedly getting married this coming weekend in Jodhpur ... which is about a 12-hour drive outside of New Delhi. Nick's been 100 percent committed to following Indian traditions leading up to the big day. Remember ... the couple had a roka ceremony at their engagement party.

They're both "all in" -- bindis and all -- as the countdown continues.