Schools will not decide on your app until your MCATs are in. Send in AMCAS now. You will begin receiving secondaries in a few weeks. When you send those in, adcoms will sit on your application but can look at it immediately once the MCATs are out in October.
Totally order your transcripts to be sent into AMCAS now. Note that you've got to start your AMCAS and print out a special form for your school to send before you do this. You designate on AMCAS that you're taking August MCAT and schools wait for that.
If you are absolutely sure you're going to apply this year (won't take a year off), you should submit now. If you wait until MCAT scores, then you'll have to wait for AMCAS verification, secondaries, etc. That would delay the application even more.