I've wandered India quite a bit with Leicas, starting in 1970 with a pair of M4s then switching to 3g and 3f models for later trips because of compactness and expense. The Barnacks were my beater cameras, not too much money tied up in case they got lifted, but with decent image quality in spite of drawbacks like squinty finder and difficult loading. For 35mm lenses I used both the old non-asph Summilux and the tiny Summaron f/3.5. There was many a time I cursed the Summaron and wished for more speed so would be hesitant to recomend too slow a lens even though the Summaron made some great images. I don't know how you will be traveling or the area, but beware of taking too much gear, it can be a mill stone around your neck. For example, if you're alone and traveling by train you'll want to take your gear along when you use the loo. Leaving it at your seat is begging to get it swiped. I know of people who have lost expensive gear on Indian trains so this is not useless paranoia. Many of the train toilets are the squat variety so try to imagine using one with a heavy camera around your neck. It's considered a no-no to pull the emergency cord if you loose your wallet or lightmeter down the hole and want to go back looking for it.... ;-)
India can throw a real mix of light conditions at you, high contrast bright sun all the way to dim bazaar lanes in the shade. Being able to handle the mix on a single roll of film can be a challenge. For B&W a lot of my stuff got processed in split D-76 to help tame the contrast. Films I used were Tri-X, and Plus-X with Agfa CNS and few rolls of Kodachrome for colour. My choice today would be Tri-X and Fuji Superia 400 asa.
These days my lens choice for travel would be (1) something wide, (2) something long, and (3) something fast in the middle.
For my M4 system this would be....
Wide... 15mm CV Heliar or 21mm Super Angulon
Long... 90mm Tele-Elmarit (the short fat one)
Fast... 35mm Summilux or 40mm Nokton
For the 3f it would probably be.....
Wide... 15mm CV Heliar
Long... 90mm Apo-Lanthar
Fast... 35mm Ultron.
Besides a single film body and lenses would probably also take a little digital P&S for tourist record shots and to conserve film. In fact on my last India trip to the south four years ago all I took was a tiny 2MP Canon P&S. Sure missed the Leica so won't leave it behind next time.
In case there's any interest here's a link to a photo essay I did in the seventies using Barnacks (3f & 3g). It follows all the stages of producing hand woven carpets. Most shots were with the 35mm f/3.5 Summaron, and yes the slow speed dial saw lots of use....
http://photo.net/photodb/folder?folder_id=611003
Other than the last shot all these were in India with a 2MP Canon P&S...
http://photo.net/photodb/folder?folder_id=611672
A helpful India travel resource is the IndiaMike web site...
http://www.indiamike.com/
India is an extremely diverse place to photograph, am sure you will find lots to aim a lens at. Have fun and remember it may take several lifetimes to see everything, that's what reincarnation is for.....
Glenn