Like all the great desert tribes of antiquity, Palm Springs Republicans deserve their own sacred text. (For the purposes of this review, Prop 13 and 'My Turn: The Memoirs of Nancy Reagan' don't count.) Jon Robin Baitz, a gay liberal humanist, has delivered them a doozy with 'Other Desert Cities,' his off-Broadway hit, which has now ripened admirably on Broadway. Power, passion, and superbly crafted palaver stippled with blowdarts of wit-this is what Baitz ('The Substance of Fire,' TV's 'Brothers and Sisters') does best. He's written his favorite sort of story, a simple tale of parents and children and blame ... in which the legacy of the Old American Century and the unsteady prospect of a new one just happen to be at stake.