I would not assume that the driver knows you are going straight because you have your foot down. I think it's safe to just assume the driver does not even see you. Either get directly in front of the driver off to one side or behind the driver. If you are next to the driver when the light turns green and get hit going straight it might be the drivers fault but do you want to get hit? I don't.
You need to be aggressive. You need to be defensive. You need to be visible.
Never assume.