Yes and no. You cannot have the medical marijuana on your person in the passenger compartment of the car.
The MMMA was recently amended to include the requirement if a qualified patient or caregiver is transporting medical marijuana it must be transported in a locked box in the trunk of the vehicle. There are some limited exceptions, but before you transport medical marijuana in your car, and not in the trunk, realize that you are subjecting yourself to the potential for arrest and criminal prosecution. If you have any questions, ensure that you have your Medical Marijuana Card (caregiver or patient) on your person when you drive, and that you have any marijuana inside the trunk inaccessible to the passengers or passenger compartment.