I am also taking the September LSAT and don't feel as prepared as I want to be, but I'm taking it anyway. First, because there is no way to get your money back at the point, and also because if I don't get the score I want, I will just take it again! I agree with @karias2895290 - I don't believe a law school will judge you for how many times you attempt the LSAT. However, if multiple tries really bother you, you can purchase LSAT preview where you will see your score early and have a few days to determine if you want to keep it on your profile or trash it.

Either way, I say take it, you never know how good you may do! Best of luck!