Weather: Hot and humid in Cochin. Hot and dry in Bangalore with cool nights. Hot, dry, and sunny in Goa. I went during the first week of April 2010, and April's the hottest month in these parts.
Food: Vegetarian everywhere. Food is classified as veg (green dot) or non-veg (red dot). Have to eat from hygienic places and drink only bottled water. Don't try the groundwater, it'll make you sick. Impossible to get good Chinese food. Possible to get some nice Western and Indian fusion foods. Pork and beef available in Goa. One and only pork shop along MG Road in Bangalore. Missed the Fenny, a unique hard liquor made from the soft part of the cashew fruit, which is available only in Goa.
Language: Malayalam in Cochin. Kannada in Bangalore. Konkani in Goa. Other than these main ones, you could try Tamil in Cochin, Hindi or Telugu in Bangalore, and Marathi or Hindi in Goa. Can get by with English for most tourist purposes. English fluency much better than China, but with a very strong Indian accent.
Cities: Bangalore's big. Goa is somewhat like Malacca, lots of villages and small towns but no big cities. From what I heard about Cochin, it's much cleaner, well-organized and friendly compared to the other two.
People: Malayali people in Cochin, they belong to many faiths - Hinduism, Islam, Catholicism, St,. Thomas Christians, other Christians, Judaism. Kannadigas predominate in Bangalore, but there are some Tamil and Marathi people there too. Konkani people in Goa, but lots of Marathis, as well as people from other states. Quite a number of Northeast Indians and Tibetans who could pass for Chinese or vice versa.
Tourists: In Goa, from all over India. Foreigners mainly Russians, with some British, Germans and perhaps a few Americans. In Bangalore, didn't see many foreigners despite the city being an international IT city. Not sure about Cochin because I didn't go anywhere other than the airport.
Scenery: Ranges from breathtaking to horrifying. Beautiful mountains, lovely beaches, vibrant alleys. Rubbish piles, dusty roadsides, broken earth. You'll see everything, and I mean everything from nicely-built bungalows to ramshackle hovels. Lots of stray doggies, but they're usually big-sized and look well-fed.
What else:
Don't bank on peaceful sleep if you're near any road. People honk all the time, just like in China, perhaps even worse.
Traffic's horrifyingly chaotic. Don't even think of crossing the road in peace and safety. Best thing to do, follow what the local Indians do and you'll be relatively allright.
If you're a foreigner, prepare to be charged higher prices than the locals for shopping, transportation, etc. Must know what's the market price for, say, a ride from downtown Bangalore to the Forum Mall or J. P. Nagar, then you can negotiate with the auto (pronounced "aato") rickshaw drivers. If you're lucky you'll meet an honest aato driver, so remember to tip him for his honesty.
People in the travel industry such as drivers, tour guides, porters, etc. depend on us for their living, so do remember to tip appropriately.
The dust will get into your nose and lungs. It's everywhere during the dry season. Can't avoid it unless you wear a face mask all the time. Unlike China, nobody wears face masks outdoors. So if you've got sinus, asthma or respiratory problems, you might want to think twice before coming.
Get a GPS. Trust me on this, it really helps. If not, buy a detailed map of the location you're in and use your inbuilt sense of direction. Otherwise, refer back to the GPS.
Try not to look too much like a foreigner if possible. Yes, I know it's easier said than done.
Get a local Indian SIM card for your mobile phone. It will make communication smoother for everybody. You'll need a photocopy of your passport, passport size photo and your hotel address in India.
It's always better to confirm everything and agree on the details before taking up any offer, package, or things like that. Make sure both sides are clear on the payment amount and expectations. Mis-communications can happen so take care to prevent them.
Perhaps I'll add more details and tips in other posts, if I ever get down to doing it. Have fun, my friends and readers.