It's better than no cardio at all. I do think that in the a.m. before breakfast is more effective though.
However, Miss Fitness Universe Katie Uter told me that when preparing for competition, they do cardio before breakfast AND after their last meal. I think the logic behind it is this, before breakfast, you are obviously burning stored fat since you have been fasting all night and you have nothing else to burn. After last meal because this will rev-up your metabolism during your night time sleep.
You taking anything to help you sleep gUiLe? Man I know it's tough and it sucks, but morning cardio makes a difference.