In Reply to: foreign cellphone in bali posted by 96822ivan on Saturday, 16. February 2013 at 09:54 Bali Time:
Yes, a Galaxy S smartphone will work in Bali. I've used my Galaxy S2 there.
The SIM question is where it will depend. Is your phone locked to a network in the US? Or did you buy the phone outright, and can use any SIM you like in it? If you don't know, find a friend on a different phone network to you and try their SIM in your phone to see if it works.
It's almost a certainty that you'll be better off with a local SIM. Roaming charges with Australian providers are horrendous and I would assume US carriers would be much the same.
As for where and how much - depends where you'll be staying, really.