If you take step 2 after you send out apps (which is early september) or if you take step 2 such that the score is not available by the time you send out your apps, you can prevent programs from seeing it. You can choose whether or not to release your score to the programs after you see what you got.
However, they have you fill in on your app when you took or plan on taking step 2. Therefore, it is possible (and perhaps others who took step 2 in this time period can opine), that while on interviews they may ask you what you got on step 2 if you should have gotten your score. Another thing to consider is if they know that you have taken it and know you chose to not release it, they may wonder why. Although, I don't know if they waste their time thinking about step 2 in such detail if you did well on step 1.
The advice I was always give was - if you did very well on step 1, take step 2 late because it can only hurt you if you already have a solid step 1. However, if you did poorly on step 1, it is a good idea to take 2 early, because people usually do much better on step 2 than 1.
And finally, another consideration - derm only has a 60% match rate, so if you don't match, even if you take step 2 late in the year, that score will be on your re-application.