I'm left handed and knit Continental in the conventional way (stitches going from left needle to right). I think lefties vary in how "left-handed" they are. There are a lot of lefties that might say they can't do ANYTHING right handed, hence the people knitting "backwards."
I found learning to knit initially awkward (but who is to say that's due to my being a lefty versus just the general awkwardness anyone would feel). But I think that knitting "backwards", while it may initially be easier, might be more confusing in the long run. If you watch me versus a righty Continental knitter, you will see that while we are doing the same thing, my left hand moves a lot more while my right is more stationary in forming the stitches. It really is a 2-handed craft, and I think that MOST left-handed knitters would probably be fine doing it the traditional way. Continental might be easier to pick up initially, but I actually taught myself English, too.
Just my 2c. FWIW, I only know how to crochet a little bit (and I don't know how to follow a pattern), but I did learn that left-handed from a lefty woman when I was about 10 years old. If I decided to start crocheting from patterns, I'm not actually sure whether that would be a problem or not.