I agree with the other guys here. Don't disclose trans status beforehand. Not only could it prevent you initially from getting the job at McDonalds....god knows if they have a problem with it, how many other people they may know in other companies they may disclose for you, making sure you can't get other jobs. You could give them preferred name, and deal with legal later. If you get the job, then check into anti-discrimination policies.
If you can't find policies, I'd say wait a while for disclosure. If you can prove yourself to be a hard worker, worthy of being there and the bosses think highly of you, this might just save you regardless.
If, on the other hand, you find you are not protected, and wish to get out of there for your own peace of mind in yourself, I wouldn't tell em. Just lay low if you can for a little bit, and set up other, better, jobs.
I've been at my company for 3 years already. Sobeys is the second biggest grocery chain in Canada. I have not been able to find their policies anywhere. I'll have to ask if I can see them soon. I am waiting for my name change to come through. That is my first step with them. I've been a valuable employee, and my dept. manager had no problem with my pending new name. If all works well and they can't fire me, I plan to transfer to another Sobeys a few hrs away.
Just be careful, and good luck, buddy. I hope everything works out for you