so i'll be completely honest...
i have a car and i have a bike. if i end up going to school in SF, i'm bringing my bike for sure. it makes life 10x easier (i.e. you don't have to deal with traffic and parking) and to be completely honest, it's as safe as you make it. granted if an accident happens, it will be worse than a car accident. however, most of the time, accidents can be avioded if you are more alert, cautious, and not riding irresponsibly. i have never had any problems, but i ride safely. it's when you start getting too comfortable that accidents happen, so basically, just never let your guard down. it's not like driving a car i think where you can zone out and still manage to drive automatically (you know what i mean), you really have to be in control. that said, i really recommend it as long as you're safe. i started on a ninja 500, i think it's a great beginner bike. it's a very forgiving bike, so it's perfect for a beginner. the problem with SF is it's pretty hilly, so you need a 500cc bike bc it has a little more torque. i thought of getting a ninja 250, but i think in SF it's really important that you have have that little extra power to get you out of trouble. it has just enough to get you by, but not enough to kill you. oh the 500 is a very comfortable ride too, not like many of these super sport bikes. well, good luck, if you need any other help on bikes or any questions, let me know.