Hi,
I'm also from Jakarta. I think there's a few anak2 jakarta on this forum!
Loads of schools do toefl courses. Before i went to study in the States i found Aim's website and took a course with them. It's <url removed by mod> . Teachers were really good. They also have an iBT Toefl simuation test, if you want to know what your level is now.
Good luck!