I called all the schools I applied to and the admissions people told me that I can send in the processing fee now, even before my AADSAS applications was mailed out.
I was advised to write my AADSAS id on the check, or my SSN #. That way as soon as my AADSAS application arrives I can be reviewed as a candidate.
Advise- call the schools and find out for your self, see if your schools want you to send in the fee now or wait. Some schools have the secondary you can download from their website, ex UCLA and fill out while you wait for the school to get the full application.