Legal Question in Constitutional Law in California

Sleep? Yes. But sexual contact of any kind -- not limited to intercourse -- would be a crime. Your boyfriend would be the criminal rather than you.

Your mother could only get in trouble if she expected (or should have expected) the two of you to engage in sexual activity and helped make it possible. Merely authorizing a platonic sleepover would not be a crime. On the other hand, if she and your father are disputing your custody or other issues, he might be able to use this visit to portray her as overly permissive and gain an advantage over her in court that way.

I agree with Attorney Hoffman's response above, and want to add that, obviously, in a little bit more than month when you turn 18, you could do anything you want with your boyfriend and sleep over there without your mom's permission. So, just wait a little bit longer.