I took the DAT without taking organic. It was very hard to teach myself that much material. I also didn't do well on the DAT. When I reapplied I retook the DAT with the benefit of organic classes. Much easier to review organic than to learn it cold, my score went up. However, I've seen threads on SDN where people claim to do fine on the DAT without the organic course. I suggest you pick up a review book and see if you think you could teach yourself organic out of the review materials and try to answer a couple of the questions in the review test. If you can pull it off, you save a year of your life if you get in on the first try.