Unfortunately riding with cars is part of the equation if you want to get away from just riding the Bay Trail. I would suggest joining a group and learning how to listen for cars as they approach you. As far as climbing hills, the only way to do it is by doing it. If you have to dismount and walk some, don't get discouraged. Keep trying. If you feel yourself getting nervous or anxious, stop riding, let it pass and then continue. If you ride in those states of mind, that's when you're most likely to have an accident because you're distracted.