This article is from the James Taylor FAQ, by Joel Risberg (firstname.lastname@example.org) with numerous contributions by others.
From Carrie Schwanke (email@example.com):
JT's song "Mexico" refers to a trip he took with his family
to this country. JT came down with the craps and a fever and didn't leave
his hotel room for the entire trip, hence, the line: "I've never really
been so I don't really know."