Both travellers' checks and cash are easy to change throughout the country, but commissions on checks can be high. Apart from top-end hotels, most places won't accept credit cards as payment although you can often use them for cash advances at western banks. Facilities for validation seem better for Visa then Mastercard. Occasionally a tattered note will be firmly refused as legal tender, and often in the smaller towns the appearance of a 1000 or 500 rupee note will cause consternation and an inability to provide change, so make sure you get some smaller notes when buying your rupees.