Hey Mat,
Just spent a week on Bintan - on the east coast at Agro Beach Resort. It was the KTA Indonesia stop and there was wind everyday. Looks like there is a couple places to kite, not just only in front of the hotel, but up the coast as well. Check out the conditions -
There's also an older Seabreeze forum post on this topic:
www.seabreeze.com.au/forums/Kitesurfing/General/Anyone-kited-Bintan-Island/
Email any of the Singapore based kite companies and they will be able to give you details too, or ask some of the local guys on Facebook - just do a search for Bintan Kiteriders.
Hope this gives you an idea - as far as I was told April should still be good riding. We all went prepared for light winds and everyone was wishing they had their 9's with them too.
Good winds
Su