Do I have to be secretive about my research until it's published?
If you act in spreading out your work without official publication, against your advisor's explicit suggestions you risk:


making a costly mistake in that you find your work being presented by others without attribution (I for sure know cases where this happened)
upsetting your advisor if the work included ideas that he wanted to accumulate credit for using in a publication
taking away the impact that a well-established impressive publication can achieve and exchanging that for a gradual acclimatisation of the community in the sense that "yes, we always knew this works, it is kinda obvious" (I have witnessed this too, namely that an idea which nobody seemed to have before, but was pushed incrementally rather than in a singular step was later called obvious)
losing credit for novelty if someone else presents it even if you are attributed; after all, the work has been presented, and your later publication will have lost freshness  (again, I am aware of a concrete example).


That being said, there are benefits of being open, namely when it is unlikely that people will claim the work, or it is hard to copy, or so exotic that people are not likely to engage in it. In this case, your problem is to convince them that it is good work and you have to permit them to acclimatise to it, anyway. Then, being open and spreading the idea to get them to get used to it is helpful. This is the counter scenario to above setting.