Puerto Vallarta, on the Mexican Riviera, isn't a one-caballo town. True, gold-sand beaches and indigo waters invite carefree bay-side relaxation. But the lush Sierra Madres beckon you on horse, mountain bike or foot and you can stroll the malecón (esplanade) with locals. Ecotourism flourishes, so visit with the dolphins, humpback whales and manta ray. The town's history is visible in the whitewashed buildings, cobblestone streets, graceful cathedral and the occasional mule trotting downtown.