If you just drag it into a 24p timeline, Premiere will blend the frame rate to that. Stays the same speed, has to render (where most stuff you do in CS5 doesn't) but it does a really good job.
If you want to slow it down for slow motion, in the media bin you can right click the footage and choose interpret setting where you can set it to 24 (23.976) and then it'll play back slowmo with no need to render.