Funny, I tried something like that initially, and it didn't appear to work. So I tried again, and now it does. I must have had a typo initially.
However, there is one issue with your formula. If you choose "2" for your second argument, then Saturday returns 6, not 7.
That argument is optional, and if you leave it off and go with the default, Saturday is 7.
So it should be: =SUMPRODUCT(--(WEEKDAY(A2:A32,2)=6))
or simply: =SUMPRODUCT(--(WEEKDAY(A2:A32)=7))