I also rely on the CDC website for such information. There are a variety of malaria phrophylactics and different ones are recommended depending on what type of malaria is present in the area. Some frequently have very uncomfortable side effects and some have no side effects. I'm not familiar with what needs to be started two weeks in advance, but several require a start ranging from 1 week to 1 day in advance of being in the area. In any event, I'd trust the CDC and/or a travel doc over NetJets on this matter.
Here's the CDC page on Mexico:
http://www.cdc.gov/travel/regionalmalaria/camerica.htm
Mexico: Risk in rural areas, including resorts in rural areas, of the following states: Campeche, Chiapas, Guerrero, Michoacán, Nayarit, Oaxaca, Quintana Roo, Sinaloa, and Tabasco. In addition, risk exists in Jalisco State (in its mountainous northern area only). Risk also exists in an area between 24° north and 28° north latitude and 106° west and 110° west longitude which lies in parts of the states of Sonora, Chihuahua, and Durango. No malaria risk along the United States-Mexico border. No malaria risk in the major resorts (that is, resorts located in urban areas) along the Pacific and Gulf coasts, although tourists should use insect repellent and other anti-mosquito measures.