Transport: Bali is notorious for its hilly roads and also for the taxi mafia. The best thing is to hire a private driver for your party. But Grab and Go Jek are both available.
Currency: Indonesian rupiahs, 20k roughly = 10 hkd, 100k roughly – 6.5 USD
In Seminyak and Canggu places would generally accept credit card. I’d also bring some USD to pay for tours etc if needed.
Sim Card: Prebook your sim card to be collected at the airport. Alternatively, you can buy it at convenience stores in Kuta or roadside which can have a better rate.
Language: Indonesian. It’s similar to Malaysian. Selamat Baggi = good morning, Thir-ree-magasi = thank you.