It could be acceptable to do this, but it would depend on certain assumptions being true.
Of course, utilitarianism says that when you are faced with two choices you should pick the one that will lead to the greatest total happiness for your society. It is okay to act in ways that might seem immoral if they will increase the total happiness of your society. In the case you present, you should lie if there will be a benefit to society that is greater than the harm you will cause. So, if you assume that African Americans will truly benefit from your actions, and if you assume that no one is actually hurt by them, you should lie to get on the jury.