The XBee Wi-Fi modules operate in the 2412-2472 MHz range.
Additional information on wifi range can be found in the XBee WIFI Product Manual at this link: http://ftp1.digi.com/support/documentation/90002180.pdf
You can find the most up-to-date version of this document at https://www.digi.com/resources/documentation/Digidocs/90002180/