You can certainly teach yourself to play to a certain level using online tutorials and any number of software programs that are sold. However, the secret to learning to play is simple: practice and repetition. To learn to play, you will be investing hundreds and even thousands of hours in practice. If you employ a teacher, you improve the chances that you are making efficient use of those thousands of hours of your time.
But it is not a bad strategy to do some learning on your own. If you are like me, you will quickly reach a point where you decide that you really enjoy it and want to optimize your practice time to move forward more quickly. At that point re-evaluate taking lessons. What a teacher will be able to do for you is watch your hands and say things like "No, no. Move your hand like this or you will never be able to play this sequence of notes at full speed." Just today, my teacher stopped me within the first 3 minutes and was able to tell me exactly what I did wrong during my past 10 hours of practice.
Good luck, I'm sure you are going to really enjoy playing.