On your back in any streetfight is a bad place to be, but if you know the technique you can kill someone with it. Certainly being choked will distract somebody. I do doubt you would have major opportunities to use it, but if the right situation came up ...
Frankly, I bash TKD because I spent five years getting a black belt from the WTTU, at high cost, and learned more about fighting in the first 1/2 hour with my current instructor than I did in all of those years.
Neither pure Kenpo or pure JJ is going to be much use for self-defense. Go for the Kenpo if that's all you've got, but I'd think you might want to look up an instructor at https://www.fighting.net.
So ... I'm a Canadian woman, 30 years old, been doing JKD and BJJ for two years. I had (no loss) a black belt in WTTU TKD and I've been a champion sabre fencer. How's that for an introduction?