Almost 3 year old not talking?

I have a daughter who will be three in September and she doesn't speak yet. She makes a ton of different noises, follows certain directions and knows how to communicate what she wants/needs most of the time, but she does not say a single real word. She's been in speech therapy for about 6 months now and nothing has really changed and in July we have an interview to get her tested for Autism. My question is this: She's starting a sort of pre-pre-school in August and I'm hoping being around all the other children will help her to start speaking...I was wondering if anyone else has seen improvements in their children or other people's children's speech after starting school.