1. Rosario left her son Carlitos in Mexico with granny to try and make a better life for herself and her son. She wanted to be able to make more money to support her family by having a good paying job. She knew she could trust granny to take good care of her son and protect him while she was gone. Rosario was able to send Carlitos nice gifts while working in LA, along with enough money that would take care of him without her there. Rosario would also gain more knowledge being in the US that would benefit Carlitos in his future.
2. Yes, it was very difficult for Rosario to leave Carlitos behind because she clearly shows so much love for him. The film shows her crying on the phone while they talk, her willingness to marry Paco to get the papers even though she knew it wasn't the right thing to do, and Rosario was also risking her life living in the US illegally. Many times Rosario considers leaving LA and going back to Mexico because she misses Carlitos so much.
3. Carlitos faced many problems living away from his mother. It was very stressful not having his mother there to raise him, and having the normal mother son relationship. It showed many times how upset Carlitos was without her, this made living day to day very hard because he was always sad. From time to time Carlitos had trouble trusting people because he felt betrayed, not only did his mother leave, but he never met his father. This is all a lot of stress on only a 9 year old. Rosario was also very upset living away from Carlitos, she felt guilty. She missed seeing Carlitos and watching him grow and change. It was hard for her not only to be away from her son and family, but to work her fingers to the bone for people who didn't treat her very well.
4. A mother in the US would normally not have to make a decision like this, but from what this movie shows, Mexican families have a stronger bond. A mother in the US would probably not work this hard and risk her life for her son and family. Mexican families normally live with several family members in close quarters and support each other. They do not have the same luxuries as families in the US so they work together to make it in life.