Marijuana

Technically no. You can't partake in public or your vehicle so unless the theater had a smoking room you risk a ticket.
"Public highway or right-of-way" means the entire width between and
2 immediately adjacent to the boundary lines of publicly maintained highways or roads
3 when any part thereof is open to the use of the public.
A parking garage is not a public highway or right of way.
Edit: It's still public though, but isn't your car an extension of your home?