I need to generate a PDF with dynamic text and I'm using ReportLab.  Since the text is dynamic, is there anyway to have it resized to fit within a specific area of the PDF?
Yes. Take a look at the ReportLab manual. Based on your (short) description of what you want to do it sounds like you need to look at using Frames within your page layout (assuming you use Platypus, which I would highly recommend).
ReportLab: How to auto resize text to fit block