Hey Daggy,
There is only one place that I am aware of that sells and does lessons etc. The Blue Oasis Beach Club in Sanur, it is run by Mario. I don't think it will be any cheaper in Bali, unless you buy a Balinese single line kite, but they dont turn or boost!

There are a few good spots to ride either in surf (reef breaks) or small beachies at Kuta/legian or Sanur which can be sketchy at low tide due to coral just below the surface

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Bali has a very short season and doesn't blow that hard generally 12-15knots with some days around 20kn.
Check it out and make up your own mind.
Good winds and Peace