Hi Indie. The place you mention is certainly not well known for being windy because hardly anyone has heard of it! The windy season is mainly June to July with some in May and August. During other months of the year there are odd windy days but not in any pattern.
Sanur is the centre for all types of kites including kitesurfing. Kitesurfing vastly outnumbers windsurfing probably because of the relative ease of travel and ease of learning. As Susan says, Oka can be found at the Blue Oasis Water Sports club in front of the Sanur Beach Hotel (now called Prama!). It is basically run by Ripcurl.
Rip Curl School of Surf | Sanur
You would be able to hire gear there if you don't have your own. You also need to be aware of the tide level as it drops to almost zero most days. You can find a tide chart at
Bali Tide Charts 2015 - exclusive to Indo Surf and Lingo, The #1 Bali Surfing Guidebook.
You need 0.8+ for kitsurfing and I guess about 1.0 + for windsurfing (the charts are based around Benoa). There is an annual kitesurfing event on Tabuan island close to Banyuwangi as it seems to be windy in that area more than most other places. There is also kiting at Canggu in waves and presumably some windsurfing too. There is more wind later in the year as you travel east towards Sumbawa, Sumba, Rote.
