NLP should I choose Python 2 or 3 (for a PHP convert)

NLP should I choose Python 2 or 3 (for a PHP convert)

I am ordering my holiday reading and among other things want to brush up
my Python skills.
Last year I did the "Learn Python The Hard Way" course and enjoyed
learning another scripting language immensely. However, the rule of 'use
it or lose it' kicked in as a result of having to earn a living (largely
PHP).
I want to pick up where I finished off and I have 2 questions for you:
The area I have identified that I want to make Python work for me is NLP
(Natural Language Processing), do the best Python libraries for NLP work
now with Python 3 or should I just stick to Python 2.x ?
Given my skillset (PHP, fairly strong OOP skills now [Refactoring, POEAA,
GoF books etc]) what is the best Python book you would recommend me?
Thanks.