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.
Gabrielle Solis is meant to be a former fashion runway model. Although she makes for a convincing print model, Eva Longoria is far too short to be a runway model (she's 5 feet 1 inch tall). Runway models are usually at least 5' 8", with Kate Moss barely scraping by at 5' 7".
In the opening credits, it is implied the male character in the artwork "American Gothic" dumps his wife for a younger woman. Of course "American Gothic" is a portrait of a farmer and his daughter, not a farmer and his wife.
Although the creators of the show kept the location of Wisteria Lane's fictitious "Eagle State" 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. When Renee Perry (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 Susan 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. However, it has never snowed on Wisteria Lane and people have swimming pools in their yards, which suggests it is a southern state. And it appears to be a coastal state since Gabrielle's second husband, Victor Lang, had a yacht at a local harbor and there was an episode set on the ocean.
Susan's last name is at first pronounced "Meyer" occasionally by all characters, before it eventually changes to "Mayer" for the second season onward.