ATMs are plenty within the city. You could easily find one on every street. There are many ATMs right at the airport.
Nearly all the ATMs accept international debit and credit cards from Visa and MasterCard. Few ATMs work with American Express cards as well.
The venue for WSC/WPC is on the outskirts of the city, so there would likely be fewer ATMs around. A quick Google search shows up 2 ATMs (HDFC, SBI) that are located about 1.5 Kilometres from the venue.
A quick note. Try to get notes of lower denominations (Rs. 500, Rs. 100, Rs. 50) from ATMs. Most of the ATMs are stocked with Rs. 2000 notes these days, and it is hard to get change for those.