First you need to finish reading the book. Then you need to define the American Dream. If it is defined as the pursuit of happiness, for instance, then your assignment won't make any sense at all. If it is defined as the pursuit of wealth, or of popularity, or of being number one at all costs, then you may have something you can work with. Once you know exactly what version of the American Dream you are going to be talking about, and have read the play fully, then you should have a much better idea of what symbols you want to focus on in your essay.
Also, don't forget to offer the sort of feedback you would like to receive on other people's threads. You wouldn't want a lot of posts here that did nothing but express agreement with the first comment made, would you?
Sean, EssayForum.com