BEST REASON TO STAY IN MIAMI FOR THE SUMMER Languid days, sultry nights Not all of us can afford to zip up to the Hamptons for six weeks of madras-clad croquet amid the cool climes and waterfront estates. Nor can we all shell out for a ticket to Ibiza for round-the-clock partying. But being rich and idle isn't all it's cracked up to be. For one thing, winging it out of town at the first hint of summer means never experiencing the true essence of living in the subtropics. Those languid days when time slows and no one can be rushed. Those sultry nights when it makes perfect sense, after the slow groove of day, to come out and play. The casual ease in securing reservations at the best restaurants. The absence of attitude. And all of it made more pleasant by the fact that the obnoxious rich are nowhere in sight.