Go and spend some time in the clubs you are considering, if you haven't already, as it might give you an insight into their whole operations and importantly the atmosphere.
Talk to some of the other students discreetly, I think when you are spending a lot of money, investing a couple of hours prior is time well spent. Obviously if you go on a bad weather day it should encourage the instructors to invest a little of their time in you without them rushing off to go flying.
As others have said don't be afraid to request another instructor, remember its YOUR money.
Good luck.