In a response that may upset federal officials, Westchester County said Friday that it plans to wait for months before getting to work on a key provision of a 3-year-old fair housing settlement. County Executive Robert Astorino is under court order to push “source of income” legislation that would forbid landlords from rejecting tenants who use federal rent subsidies. The county is appealing to the 2nd U.S. Circuit Court of Appeals, but the appeals court has denied a stay. On Aug. 10, federal Judge Denise Cote gave the county a week to disclose its plans to comply. The county’s response, in an email sent late Friday, said the county will wait until the appeal is decided before taking up the legislation. Oral arguments on the appeal are unlikely before October.