Palm Beach habitués tell us residents are getting the royal treatment next week. Seaside spies say Rosita Spencer-Churchill, the Duchess of Marlborough, will hit town with her brother-in-law Prince Max of Bavaria and sister Princess Elisabeth. John and Marianne Castle will host a bash for the duchess at their home, formerly the “Kennedy Winter White House.” The royals will also be guests of honor at a separate party hosted by Pepe and Emilia Fanjul with Netscape founder James Clark and his wife, Aussie model Kristy Hinze. Violinist Itzhak Perlman is scheduled to provide entertainment at Clark’s 40,000-square-foot South Ocean Boulevard mansion, previously owned by Janet Annenberg Hooker. For Palm Beach partiers whose invites were lost in the mail, we hear hot spots this season include Table 26 and Asian spot Echo, which one seasoned resident says has been filled with “some of the most beautiful girls in Palm Beach . . . beautifully dressed, long legs and high heels,” plus, “lots of good-looking men at the bar.” Noted!