Small Business Disaster Assistance Act of 2011 - Reduces temporarily, through September 30, 2014, the interest rate on the federal share of certain Small Business Administration (SBA) disaster loans (to repair, rehabilitate, replace, or refinance property damaged or destroyed by or as a result of a natural or other disaster) made to businesses on or after August 26, 2011. Sets forth temporary rates of: (1) 1% per year, in the case of a business concern unable to obtain credit elsewhere; and (2) 3% per year, in the case of a business concern able to obtain credit elsewhere.