Hey telejojo - thanks for checkin' out the thread.
Monument Valley is about 300 miles (~ 5 hours) from St. George. Might be kind of far for the Zuma!
St. George is in the far southwest corner of Utah (mostly north from Las Vegas). Monument Valley is on the southern border of Utah with Arizona, but close to the southeast corner, past Lake Powell. Great roads and (high speed) riding, but a long ways.
Hopefully your wife likes the Zuma. Great scoots for around town. Happy riding in 2013!