Hedge your bets, don't book any accom until you get there. Plenty of places to stay and that way you can check the forecast and make the best decision.
If you book now you may be reading other peoples stories of goodness somewhere where you are not
Mid August a couple years back wasn't good for me..staying in Kuta..first 3 days were flat all over, Then next 4 mornings I surfed onshore outer reefs while on the other side ppl had a ball... clean barrels at keramas..funny weather
Been there heaps in Sept/Oct. Yould still get epic surf without the April-June crowds. I take it that if your going for a boys trip there will be plenty of Bintangs involved.... Id say stay on the bukit somewhere, heaps of waves within 10 mins especially if your a bit slow getting out of bed each morning. Plus heaps of accommodation there too and pretty cheap.