I live with my mom and I want to live with my dad but she won't let me they split up when I was little my mom has had me for 15 years and I want to live with my dad so I want to know how old you have to be to pick who you want to live with

You can choose when you turn 18 ( at least in the US)

Before that, your dad will have to file in court and make a motion for a change in legal custody. This will effect child support payments and other issues. Also the judge may not allow it, your dad will have to show how this is good for you, and his ability to care for you.

Your mom can show why this should not be allowed, then the judge will decide

Am 15 years old and I live with my mom in California and I want to live with my dad in mexico but she won't let me is there anything I can do to live with my dad

Do you know why she's against it?

Are there court orders for where you live?

No I don't know why she's against it and no

Please stop creating new threads for the same question.

There is NOTHING you can do. Your dad has to go to court to change the custody order. At 15 your preference will be listened to, but it is the courts decision.