Although the creators of the show keep the location of Wisteria Lane a secret, several clues have been given that contradict each other. For example, in the first season the restaurant Saddle Ranch is featured once, suggesting that the mystery location is either in California or Arizona, where the restaurant has locations. However, two families, the Applewhites and the Mayfairs had moved from Chicago suggesting that Fairview is near there. Those two cities are very far from each other. When Renee (Vanessa Williams) arrives she tells Lynette that she flew all the way across the country to see her. Renee lives in NYC so that would suggest Fairview is on the west coast of the United States.
There is also a scene where Suzy is looking for her ex-husband's grandmother's ring. You can see a sign for US Highway 7 which runs from Norwalk, CT, to just south of the Canadian border in Vermont.