I intent to travel to US from India in the last week of September 2016 for 20 days and have valid US visa till November 2016. Will this visa be acceptable ?
You should be ok. US visa validity works a bit differently than you'd expect, the expiry date is the last day you can travel to the US and the duration of stay is determined at the border by the immigration official.
Here's what the State Department has to say (emphasis mine)
What the Visa Expiration Date Means
The visa validity is the length of time you are permitted to travel to a port-of-entry in the United States.
A visa [...] can be used from the date it is issued until the date it expires to travel to a U.S. port-of-entry. [...] the visa expiration date shown on your visa does not reflect how long you are authorized to stay within the United States.
Admission to the United States and your Duration of Stay
Upon arriving at a port of entry, the CBP official will determine the length of your visit