Gotta disagree with Marni (the advice she gives is sound for areo bars, not drops) - around corners, down hills and in groups is *exactly when* you need to be in your drops. It's not just another riding position, nor is it just for less wind resistance. You want to be down there for more stability and more control.

Always ride in your drops when taking a corner at speed and when descending. Get comfortable doing it, because it is the safest place to be in these situations. Racers ride in their drops when going fast in a pack, because of the better control and because it makes it more difficult to hook handlebars with another rider.