Are you looking to learn the ops side or just want to play with Hadoop to learn how it works and how to use create jobs?

If you want to learn the "ops" side, EC2 is great for building clusters, tearing them down, testing different configurations, etc.

If you just want to learn how to start using Hadoop, writing jobs - don't even bother setting up a cluster. You can use it directly with Eclipse to run a single-node setup on your machine. Way less complexity and much easier to start learning with.