Yes BB is open in OCT. Every year Disney closes one of the 2 waterparks for maint. this year TL is scheduled to close mid oct. Next year BB will be the one to close. As for being warm enough, thats personal preference, for us it was perfect for others it could be on the cold side for swimming(low 80's). Last year we were in disney from 10/25-11/3 and BB was closed and TL was packed!!! So if you do plan to go and they are down to one water park go first thing when they open to be able to find a spot to put your towel!