Continuity mistake: When Selena is singing "Como La Flor" in Mexico after the crowd was pushing into the stage, her mouth doesn't match the words to the song. Her mouth is a few words ahead of the song.
Continuity mistake: When the two Mexican guys are driving down the road to Selena, in the first shot where you can see their faces, the guy who has his hair combed back is on the passenger's side. Yet, when they stop for Selena, the guy with his hair combed is the one driving.
Continuity mistake: After Selena draws the cowhide trouser outfit the scene is where they're performing in them. In one shot her belt is secured to her waist and in others it is hanging.
Continuity mistake: When Selena's father and mother are arguing over the kid's first performance, Selena's mom's hair first is in front of her shoulders, than behind, and it continues like that for the duration of that scene.
Continuity mistake: When the bus gets stuck, the sun changes sides throughout the scene. First, it's on the passenger side of the bus, then in front of the bus when the two guys in the car stop to help, then on the driver's side of the bus during the rescue attempt from the guys.