So I was planning on taking up a karate class, now I don't know if this style is effective as a self defense?
Meaning do they teach you skills and where and how to use them?
A lot can have to do with the instructor rather than the style. I study and teach Shitoryu myself and one of the things that I like about it is that some Shitoryu groups have taught jujitsu and ground fighting for years and incorporated it in with the style itself long before the advent of MMA. It is thought of as a more contemporary Japanese style than some of your older Okinawan and Japanese styles like Shorinryu or Shotokan and among other things stresses keeping the elbow bent slightly on punching and some blocking as well as the use of angles when fighting. It takes a fifty/fifty approach to punching and kicking and its kata are traditional in nature and stress a little deeper forward stance than older styles do. While I am partial to it myself because of their more contemporary approach to things and incorporating jujitsu and ground fighting into their training not every instructor does that as there are several different governing bodies of Shitoryu now. It like many other styles has suffered from politics, greed and a difference of opinions about different aspects and so I always say shop the school and instructor and not the style.
I have never studied Shito Ryu but have trained in the Okinawa Karate arts for many years. I have a bunch of friends who study Shito Ryu and they are all really decent at it. Make sure you chose the art you are going to study based on the quality of the instruction over the name of the system being taught. Just remember that is much more to studying Karate than just learning to fight or self defense. This is what makes it an art form instead of sport. Good luck.