I read this book recently, the author is Lois Pryce, she's a journalist from Great Britain. She rode from Alaska USA to the tip of Argentina on a motorcycle. Most of it she had a companion of some sort, but a lot of it was traveled ALONE.
Fascinating adventures going through Mexico and Central America, something I would do only in my dreams, especially since I have the MS and meds to worry about (yeah, and try to find Depends in Nicaragua...).
~Kim in NV