Some of our customers are playing left handed and find the GT videos very easy to use. They say you should just pretend the video is a mirror. Read all about it here:
http://www.guitartricks.com/forum/showthread.php?t=38434
Unfortunately, the majority of our lessons are for right handed players. Most lefties I know are transcribing and transposing to left-handed notation. This actually increases their music reading ability very quickly.
If you are a beginner, we would suggest learning to play right handed since you use both hands anyway. And you'll be better adapted on your fretting hand, which is the one that does most of the intricate work!
Jon Broderick, the Guitar Tricks founder is a lefty himself, and this is how he learned. We don't have any lessons available for the left hand position, though.
Hope this helps!
If you have any questions, comments, or concerns, please contact us.