If you'd be there right after the lower level AP blocks end, it could be pretty crazy. Especially this year, if even any one of Railroad, ROA, TSI or F! reopens while they're blocked, people will stream back in. Disney also did an AP Days promotion in August/September last year and probably will again this year. On the other hand, the Halloween crowds start earlier and earlier this year as more parties sell out and people start coming earlier to go to the parties and on non-party days to avoid them. The weather can be equally hot into October as August, but I'd still probably take October for Halloween time and the likely chance that some days will have better weather than most of August.