BCV - a wonderful location! We used to stay there once in a while, but in recent years, it's been very difficult to book.
Call MS immediately for May and ask about availability. That's the only advice I can give.
As far as September is concerned, call at the 7 month window. I'd call day-to-day and book individual days if I were you (you can then combine them when you get the week/days you want).
With the absolute explosion in memberships at SSR and now AKLV, the BCV are a hot commodity. It's a small resort with limited rooms and a dynamite location.
If you can't get into the BCV, you cannot use SAB. Sorry, they're pretty strict about it.
BWV, BCV, SSR
June-July - Universal's Royal Pacific & GF CL
August - VAKL
President's Week 2014 - BCV