Regardless of how "good" this place claims be be regarding their instructor training, you still aren't going to know what the heck you're doing until you actually start teaching. After about 50 hours dual you'll start to get a clue, and after 250 you'll start becoming competent. After about 500 you'll probably be decent at teaching.

Some good advice for you:

You live in Florida, where there's plenty of schools to choose from. Call around to five schools in your area and see how much they quote for the CFI/CFII. You'll quickly find that $17,000 is way out of line. If you live near Palm Beach, PM me and I'll tell you a good school to go to that won't rip you off.

As a reference, almost three years ago I spent about $2,000 for my CFI, and after a few months of teaching, the flight school paid for my CFII. These days the school probably won't pay for your CFII, but still it should be very cheap (after about two flights, I was ready to take the CFII).

Also, DO NOT get your CFII right away. Spend some time teaching primary students with your CFI first. This will give you the experience of teaching while also building up your list of clients/students. Then, when you start working on your CFII, you'll have the benefit of teaching experience. This will make the CFII the EASIEST rating you've ever added. You absolutely need to have some decent teaching experience before you start teaching instrument students anyway. These more advanced students will become very frustrated and irritated if they sense that you don't know what you're doing. At least you can somewhat pretend you know what you're doing with a primary student until you get a little bit of experience.