It is available for a free 14 day trial. You'll need to enter a key to use it past 14 days.

There is a free version called Tableau Public. While the product has almost all the same capabilities as Tableau Desktop, all work that is saved is immediately publicly available, so if you have some confidential data, you would want to be careful with it. That being said, it's great for building a portfolio, for learning Tableau, etc. It's a truly wonderful product.

So the question would be how do you intend to use Tableau?