The safest places to change your money ar at the Indonesian banks.

The best rate is on the street, you will find lots of places to change money in Kuta, etc.
Be sure you count the money you receive as there are quite a few money changers that try to rip you of.

In Febr. $100 US was worth 930.000 Rupiahs.

The first money changers you encounter are when you exit customs.

Don't forget to keep 100.000 Rp. per person for the Departure tax.

Have a great vacation.

Casey.