Being named as the Acting Director of an operation can be both a curse and a blessing.
On one hand, you have the power - at least most of it - to demonstrate your skills and if you are interested in becoming the permanent director, you'll have an advantage over your rivals. On the other hand, since you are in an acting capacity, your power may not be seen as full and some individuals and departments may not provide complete support or cooperation because of what they regard as your quasi-lame duck status. You have the opportunity to succeed but you also have the chance to screw things up.
My advice is to act as if you are indeed the director but to refrain from pressing the question of when the ultimate selection for the job will be decided. Time is on your side. The longer upper management procrastinates on filling the position, the stronger you will be. You'll have a greater list of accomplishments while in that job; you'll have built up better relationships with other key players in the organization while in that position; and people will begin to think of you as the real director and not simply as an acting one. This latter point has the added benefit of scaring off potential rivals who will interpret management's delay as a signal that the folks at the top plan on naming you anyway and that any outreach efforts will be simply pro forma.
The worst thing you can do, aside from creating a disaster or picking fights, is to drift. You've been given a grand opportunity and if all you are doing is simple office maintenance, management will have a legitimate reason to question your creativity and your judgement. See which procedures can be streamlined, survey your internal and external customers on ways to improve your area, talk to employees about things they'd like to see changed (and those which they hope won't be altered), form new networks to increase professionalism or increase the unit's profile, etc.
In short, show them that you are a serious performer.
Go out of your way to avoid conflicts with your new peers. Management hates fights and you'll be at a disadvantage both in status and in knowledge of the personalities. Your goal is to be perceived as both creative and reliable, not as a disruptive radical or an immature player.
Be friendly and reasonable. Erase any tendency to be sarcastic. Save your wilder ideas for a better time, such as after you've landed the job. In the meantime, your job is to reassure upper management that the job is in good hands, matters are under control, and you have the social and political skills to succeed at a higher level.
Now is the time to be at the top of your game.
Don't plan on showing them what you are capable of after you've gotten the job.
Do it now.