Alberto Esquivel had intended to build a family home in the foothills of Costa Rica’s Talamanca Mountains, a modest country abode where his children could ride Andalusian horses among grazing cattle. Five years after breaking ground, the Costa Rican native has instead created Hacienda AltaGracia, Central America’s most exciting and authentic new luxury resort. Opened last June—and operated since July by Auberge Resorts—the 860-acre property offers a true taste of Costa Rica with morning hikes to see sloths and…