Whether you consider yourself to be "ITF" or "WTF" (if these are even things one could be) is hardly any matter of importance. These are nothing more than titles of organizations and any differences that may exist between organizations mean absolutely nothing to students or the instruction of Taekwondo.
It's important to stress that last part: They have nothing to do with the instruction of Taekwondo.
That's not to say that there aren't acceptable uses for the ITF/WTF/ATA/etc distinction. Because different organizations use differing pattern sets, it is frequently useful to describe one's pattern sets as "ITF" or "WTF" patterns (as we do throughout this site). Because these groups and their subsidiaries frequently have consistent tournament rules throughout their organizations it is common to hear of "WTF style sparring" or "an ITF tournament". These are all fine and good. But they are only good as labels. Labels provide a useful way for people to communicate ideas. Labels are not the things themselves. The WTF or ITF have nothing to do with the side kick that you're capable of delivering. They have nothing to do with the way you snap to attention and bow when your master instructor walks out onto the training floor. And they certainly have nothing to do with Taekwondo, in the truest sense of the word.
Let's qualify that last sentence. If you think Taekwondo is a sport, then what we've said is wrong. If you think Taekwondo is an art, then what we've said is wrong. But if you think, as we do, that words like "sport" and "art" are merely labels, then you'll probably realize that Taekwondo, in addition to being another label itself, is none of these things. It is the relationship cultivated over months, years or a lifetime between you and your instructor. If the absolute worst were to happen to you and you were to lose everything you had in this life -- your job, your money, your home, your family, even the clothes off your back -- you would still have Taekwondo. It is something that no one can take away from you.
Life is all about building these sorts of relationships. They are the only things that last. When we lose a loved one, we frequently say that "their memory persists". What do we mean by that? It's not their body, it's not what they happened to leave you in a will, it's not the photograph of them that sits on your desktop. It's the relationship that persists. If you study Taekwondo in earnest from a qualified instructor, you'll find that Taekwondo is so much more than kicks and punches. It becomes part of who you are. We might tell someone we've just met, "I'm an accountant" or "I'm a waiter". These things aren't to be taken lightly. If the accountant lost everything -- his home, his family, etc. -- he'd still know how to be an accountant. If he spent any significant amount of time pursuing that title, then it will always be something that contributes to who he is. Taekwondo is very much the same. Taekwondo is a relationship you build with yourself. It's a relationship of development and growth. And it is something that can never be rescinded or forcibly removed. It is who you are.
Although we've all heard the saying "can't see the forest for the trees", few people understand that Taekwondo is not any one thing. It is hardly a thing at all. There are thousands of people studying and sharing the martial art known as Taekwondo. And every one of them is different. Step back and see the forest for what it is. Take note that the relationships that matter are between people and that they are not independent, but interdependent.
What does all this have to do with the I.T.F. or the W.T.F.? Nothing. And that's the important point to remember. When you're choosing a school, an instructor or a workout partner, their affiliation means absolutely nothing. You are not cultivating a relationship with the I.T.F. or the W.T.F. If either of these organizations were to suddenly dissolve and cease to exist it would cause no pain or suffering to (virtually) anyone. If, however, you were to lose an instructor under which you trained for five, ten, fifteen years, then how would you feel? Life is all about building genuine relationships. No one is going to be lying on their death bed wondering how their life would have turned out if they had only joined the I.T.F. instead of the W.T.F. (or vice versa). What matters most is who you are and how you've related to everyone else in your life. This truth is just as much a part of Taekwondo as any punch or kick.
NOTE: For practical guidance on choosing an instructor/school, please see this document.