You CAN get tickets a few days ahead of time or day of, online...which is probably good for "..Baby Jane"..and probably essential for "Valley of the Dolls"..
They don't use a huge theatre so getting there early, even if you have tickets, is not a bad idea.............
And make sure you go to the 7pm show. They often add a 10pm show but that costs ten bucks and DOES NOT include Hedda Lettuce. I did Baby Jane and Mildred Pierce last year and it was a blast. Can't wait to see it again.