I was in the same boat last year, and I thought it would make sense to start out on Python 3. However, my intent was to learn Python to use Django. Django still isn't ready for that, so I'm using 2.6.

On the other hand, the text adventure game I'm writing for fun/as a learning exercise works great in Python 3, as it doesn't have any external dependencies.

Therefore, it depends if you're learning it for a specific use or just because you'd like to learn Python.

Read over http://docs.python.org/release/3.0.1/whatsnew/3.0.html for an overview on the differences. There are a few incompatible changes, but to say 2 and 3 are two different languages would be a big stretch.