Traveler's Diarrhea: This is the most likely diagnosis given the patient's recent travel to Mexico and symptoms of nausea, vomiting, and diarrhea. Traveler's diarrhea is a common condition caused by consuming contaminated food or water, and Mexico is a high-risk destination for this condition.

Viral Gastroenteritis: This is another possible diagnosis, as viral gastroenteritis can cause similar symptoms and is often contracted through contaminated food or water.
Bacterial Gastroenteritis: Bacteria such as Salmonella, Shigella, or E. coli can cause gastroenteritis, which may present with similar symptoms.
Food Poisoning: Food poisoning from consuming contaminated or spoiled food can also cause nausea, vomiting, and diarrhea.

Cholera: Although less likely, cholera is a potentially life-threatening condition that can cause severe diarrhea and dehydration. It is essential to consider this diagnosis, especially if the patient has been exposed to contaminated food or water.
Giardiasis: Giardiasis is a parasitic infection that can cause chronic diarrhea and is often contracted through contaminated water. Although less likely, it is crucial to consider this diagnosis to avoid missing a potentially treatable condition.
Intestinal Parasites: Other intestinal parasites, such as Cryptosporidium or Cyclospora, can cause similar symptoms and should be considered in the differential diagnosis.

Brucellosis: Brucellosis is a rare bacterial infection that can cause gastrointestinal symptoms, as well as fever, fatigue, and muscle pain. Although unlikely, it is essential to consider this diagnosis if the patient has been exposed to contaminated animal products or has a history of occupational exposure.
Ciguatera Fish Poisoning: Ciguatera fish poisoning is a rare condition caused by consuming contaminated fish, which can cause gastrointestinal symptoms, as well as neurological and cardiovascular symptoms. This diagnosis is unlikely but should be considered if the patient has a history of consuming fish in Mexico.