Visiting Bali Ubud

Carrying too much cash is always a bad idea so cards and a few traveller's cheques are a better bet.
If you do carry Dollars, check the maximum amount allowed into Indonesia before you travel and use hidden wallets in order to keep it safer. NEVER flash more than you need in public as there are some people in Bali who could target you for theft.
Dollars for exchange means new crisp bills, not old tatty ones as a lot dislike accepting them.

All the cards with Visa, Mastercard and the other usual logos work in ATMs here but I'd stick to BCA and BNI as I can assure you they work pretty much every time with no issues.
Other banks are probably fine but these two are the ones I stick to.

One more for cash and traveller's checks, use XXE money converter site to check the mean rate the day you intend to exchange so you have a base point to work on.