There is a straw poll where you can vote for Rand Paul.
Many libertarian leaning groups have been driven out of CPAC in the past few years. The Libertarian Party will not have a booth there. Not sure about Campaign for Liberty.
Breitbart, the Capitol Research Center, and other groups of interest will.
If it's like last year shuttles will take you for free from Union Station and the GWU/Foggy Bottom metro to a Prince George's County.