At Indira Gandhi International Airport: http://www.newdelhiairport.in/category-shop-and-eat.aspx?id=3&category=Forex.
Online currency converter: http://www.delhitourism.gov.in/delhitourism/travel_tools/currency_converter.jsp
EC cards are accepted at most shops and restaurants. Credit cards like VISA, Master Card and others are widely accepted. At ATM machines all over Delhi money can be withdrawn using debit and credit cards.
Further information can be obtained from:
English and Hindi.
Opening Hours depend on what category you are looking for. In general:
See more information about markets in Delhi on the Tourist information page.
Check the below websites for guidelines for visitors:

Since 2008 Restaurants, Bars and Clubs are non-Smoking areas. However they might provide a separate smoking area. But Smoking is banned on public transport and in hospitals, airports and public and federal buildings.
Most of the hotels provide free WLAN, check with your Hotel. Several places and Cafes or Restaurants such as Starbucks are offering free WLAN as well.
The month of September is characterized by essentially constant daily high temperatures, with daily highs around 34°C throughout the month, exceeding 37°C or dropping below 30°C only one day in ten.