We recently went to Bali with our 3.5month old.(We travelled with a group of friends and there was also a 5 month old and a 7 month old.)
I am BF and found that my daughter needed extra feeds due to the heat- mainly in the middle of the day. She doesn't take a bottle so wouldn't take water. I hired a steriliser (expressing due to oversupply!) from www.balibabyhire.com and found them to be very helpful. The steriliser was clean and dropped off at our hotel at the agreed time. It worked out to about $23 for the weeks hire + $50 deposit. (The company can also organise a car with a baby seat.)
I would recommend taking a mosquito net to cover the cot as some hotels don't have them, although ours did. You can pick up a cheap one from Big W. We didn't use mosquito repellent due to the age of our daughter, instead we used the sun cover when in the pram and sprayed repellent on that. (She only got bitten twice)
We also took all our nappies and wipes etc. You can buy them there but apparently the quality isn't the same and I didn't want to risk leaking nappies! We also took huggies swimmers nappies- not sure that you can buy them there. I bought disposable bibs from Target as back ups- I didn't want to wash bibs in the water and then have my daughter suck on them. We used Fess Noses a couple of times due to the aircon in the room- we had to turn it down to low at night.
My friends whose daughter was on solids also took jars of food with her.
The Balinese love kids! We often had waitresses begging to hold our daughter while we ate our meal. My friends also used babysitters organised through their hotels and were very happy with them.
If you have any other questions let me know and hopefully I can help you out.