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.
Xiao-Mei would never be able to be a surrogate without having a child of her own first. All reputable surrogacy agencies in the US require their surrogates to have had at least one full-term, live birth before becoming a surrogate.
Several times through out the seasons, when the camera is filming from the outside of a house into the front door, it can be noticed that the interior that is visible from the shot is different from the interior when filming on the inside of the house.