Hey, if you can even THINK of training for a half marathon, you must be in fairly decent shape. I know that i wouldnt even be able to stand for half an hour.
I know its a shock to the system to take the bus, but i have been doing it for ten years now, and i almost prefer it. No, you cant run out and be back in an hour like with a car, but it does force me to walk a few blocks at least a few times a week.
I'm rootin for ya!