What do you do for excitement after you and your wife have made adventure travel history? If you're Dana and Ginger Lamb, authors of "Enchanted Vagabonds," you put away your famous canoe, turn away from the sea, and march inland, bound this time not for the misty green waves of the Pacific, but the forbidding green hills of the unexplored Mayan Jungle. "Quest for the Lost City" is the story of how the Lambs returned to their old Spanish speaking haunts. Only this time they were not roaming in general. They were seeking in particular for the source of a legend, the fabled lost city of the...