Answer:
De Vaca's 300 men faced several setbacks during their expedition, including harsh weather conditions, lack of food and water, disease, and hostile encounters with indigenous peoples. They also faced challenges navigating the unfamiliar terrain, which often slowed their progress and made it difficult to find food and water. Additionally, they encountered resistance from the Spanish government, who were skeptical of their claims and reluctant to provide them with the resources they needed to continue their journey. Despite these setbacks, de Vaca and his men persevered and were able to complete their expedition, albeit with significant losses along the way.