We have done, I think, four trips in late November and early December. We had generally good weather, with much more sun than clouds/drizzle, except one of those trips when we had two or three rainy days in a row.
We just returned from a trip (late July), and it was mostly sunny, with a few cloudy times and what we felt was quite a bit of wind compared with our Nov.-Dec. experiences.
A local said he was of the opinion that the best weather on average is late July through early November, his theory being that the conditions that are conducive to forming hurricanes elsewhere in the Caribbean somehow help to keep Bonaire's weather nice.
I don't think there is any month when I would be hesitant to go.