To answer your original question, we have been in September a number of times and (of all the times we have been) have never queued for more than 30 minutes for any ride, apart from Dumbo - but that is the slowest moving ride ever!. Mind you, we choose not to go during high season and we have so far managed to avoid France holidays.
It is busier at w/ends, obviously and at around 4 pm it will start to get noticabley (sp) busier because of the warmer weather in Sept and may French have annual passes so go after school etc