Revealing mistake: In the scene where Captain Love and Antonio Banderas (as Zorro) meet in the hallway of the hacienda, two guards rush down the hallway and drop their rifles and swords. Zorro asks them to bend over and then proceed to kick/nudge them out the window. If you watch carefully, you'll notice that the guard on the right (furthest from Zorro) reacts to the kick too early. (01:33:30)
Continuity mistake: When Edwards is teaching Hunt the alphabet, whenever he turns it around or you see it from another angle, the upper and lower case changes.