Traditionally, Key West was one of those end-of-the-world places that attracted those who were keen to get away from it all. (I always get a kick out of seeing the signs for mile 0 that mark the beginning and end of Route 1.) For many years, it was a refuge for artists and writers — most famously, Ernest Hemingway, but also Tennessee Williams, John Hersey and Elizabeth Bishop. More recently, Key West acquired an off-putting reputation as a venue for vacationing college students, and the main thoroughfare, Duval Street, still has a stretch of a few blocks that can be politely described as raffish. Lately, however, there has been an influx of well-heeled retirees, who have restored cottages and raised the prevailing tone.