When Max tells Sergeant Valdez to raise the Mexican flag over the Alamo, the pole is clearly shown as being beyond the perimeter wall, however when the flag is raised, the pole is mounted on the side of a building- easily reached from inside.
Max and his second in command are on ladders looking over the wall of the Alamo. In a face on shot Max has his left hand on his face. In a shot from the left his hand is on the ladder and in a side shot from the right his hand is on his face but two fingers are curled into his palm.
The "military" helicopter used by General Lacomber has a civilian registration number on it.
Laredo is 146 miles from San Antonio. While Max and Gomez get to San Antonio by car, it's never explained how the rest of the men get there.
Max tells the border agent he and his men are headed to Laredo. Max would know Laredo is just 300 feet from the Mexico-Texas border, and can be accessed from the Laredo Convent Avenue Port of Entry. However, the border crossing Max leads his men to is in the middle of nowhere.