1) there's no point not wearing your headscarf then start wearing it once you get your job as firstly the men who you hide from will have already seen your hair, and secondly you need to stick to the character they hired
2) if you are concerned that its going to get in the way of your career, then you need to prioritize what's more important, by not wearing a hijab it won't mean you don't follow islam, all religions make some sacrifices to fit into western society
3) Just be yourself...with or without the headscarf....just wear what you think would be appropriate, in my totally honest opinion....i would probably leave the hijab at home, but in no way does that mean you're not a muslim