Do they speak English in Bali?
Where English is easy
In the main tourist zones, English is genuinely the working language of tourism. Most Balinese who deal with visitors speak three - Balinese, Indonesian and English - and menus, signs, booking apps and ride apps are commonly in English (bali.com, Nomadicated). For a standard beach-and-cafe trip you will rarely hit a language wall.
Where it thins out
Head into rural villages, local-only markets, the remote north and east, or sites that draw mostly domestic tourists, and English can drop away fast. A translation app with the offline Indonesian pack (Google Translate) covers the gap nicely. Worth knowing: Balinese is a distinct local language, while Bahasa Indonesia is the national one - the useful one to pick up a few words of.
Phrases that earn goodwill
You do not need them, but they land well: terima kasih (thank you), tolong (please), permisi (excuse me), berapa (how much), enak (delicious). Locals warm up quickly when a visitor makes the effort. So the honest answer is that language is not a barrier to a Bali trip - claims that you "must" learn Indonesian to get by are n/a - but a little courtesy goes a long way, especially once you leave the tourist strip.
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