I really can't say enough about what an incredible experience this is. The idea of improv is intimidating but the students and teachers are so supportive that this falls away after the first class. The skills and ideas you learn are shockingly applicable to daily life and, most importantly, it is crazy fun.
I'm currently enrolled in level B and look forward to continuing. Don't let fear hold you back; it is something you'll wonder why you didn't do before.