Which all places in South India do you intend to visit and what is your usual subject? If it's primarily nature + architecture / monuments with some candid shots thrown in here and there, I would suggest films like Provia and Sensia [the non-pro Provia] 100. Like the rest of the country, South India is also full of bright colours and hence even less saturated films will do the job perfectly. I would not vouch for saturated films as those will have a high potential to ruin the portraits taken there. One word of caution - it is unlikely that you will get a ready supply of your slide film of choice at most of the photo shops in the country. So come prepared with your stock. If you have specific questions, feel free to drop me a PM as well.

Cheers
Deb