Do I have to bring someone along, or can I drive after the buttocks lift?

You need a ride home. Buttock lift is a serious surgery. You definitely need someone to take you home and stay with you for at least 24 hours.
No driving. First you will probably receive medication which would alter you judgment. Second, driving would put you at risk for disruption (dehiscence) of your wound. So no driving.
You can't drive. After an aneasthetic until the next day at the earliest. Plus, you don't need to be sitting on your implants till okd by your surgeon.
Bring someone. If you receive a sedative during your surgery, it won't be safe to drive home, even if you think you feel fine. Moreover, you may be sore and you may want to alter your position making driving more difficult. Finally, your reflexes may be slower than normal if your bottom is sore.