They do indeed; I believe the NH Libertarian Party chairman John Barbiaz is a FSP Porcupine, or possibly, like NH Governor Benson, signed on as a *Friend of the Porcupines*.
I don't know what their numbers are, but I bet you can find out from the link. NH listed 242,028 registered voters as undeclared, 36.8% of their total, in the 2000 election, second only to the Republicans and well ahead of the Democrats in a distant third place. And soon, perhaps fourth....
Not all of those *undeclared* are Libertarians, of course, but I'd expect that most Libertarians are so registered. And it'd certainly be a good number for the Libbies to shoot for.
But I'd expect most Porcupines to register, if not necessarily vote, as Republicans.