5 weeks at the Marriott? Thats kind of long and you'll get bored with the area - my parents' home is a five-minute walk from the Marriott so I speak from experience. Spend a few days in the South Goa hotels (better beaches) or the North Goa beaches (better nightlife and dining).

1. Car: Both Hertz and Budget have offices in town. Ask the hotel for contact numbers. I've used Joey's Car Rental at +91 832 2228989 or +91 98221 02829). All of them offer an option with driver at not much more than self-drive. Rates are Rs 1000-2000 per day depending on the type of car. If you are driving, watch out for traffic cops at night on the roads leading from the north Goa beaches to Panjim - they've been cracking down on DUIs the last couple of years.

2. Clothes: Branded clothes aren't that much cheaper in Goa, but there are plenty of places to buy general casual stuff that you can throw away after your trip. There's a couple of laundry places in the area as well if you want to save on hotel laundry. Ask the concierge or the taxi drivers hanging out outside the hotel entrance.

3. Tips: http://www.flyertalk.com/forum/showt...highlight=tips
I've used credit cards in restaurants and retail outlets with no issues. Always carry cash with you though.

4. Mobile: I use Airtel prepaid SIMs (GSM) which has excellent coverage throughout Goa, including beaches and highways. There's a counter at the airport near the baggage claim where you can buy a prepaid SIM. Their customer service sucks though.
Reliance India Mobile (CDMA? WLL? Definitely not GSM) offers a data service as well - there's a Reliance Web World outlet with a broadband internet cafe about ten minutes walk from the Marriott - ask the hotel for directions.