Most people from outside of Northern California and Southern Oregon will fly into Redding, CA, San Francisco, CA or Medford, OR and make the drive from there. It's about a 5-6 hour drive from San Francisco up highway 101. If you want to see some of the most beautiful terrain on the planet and have a couple extra hours, head up highway 1 along the Pacific coast. You might need some Dramamine from all the twists, turns and switchbacks.
Here's Rick Burneson's experience at the 2002 Fray. He drove from Southern California.
Old Weird Harold (I think) talks about his trip to the 2003 Fray, which took place in a new, larger venue.
One industrious race, Tom Bowman of BRP rode his motorcycle from Virginia to the Fray in 2008. Here's his article on the experience.
Here is racer Smalltime's account of his experiences at the 2011 Fray.
I swear I'll make it up there someday.