Vallarta-Nayarit on Mexico's Pacific coast is poised to become the country's hottest new vacation destination. Vallarta-Nayarit attracts a diverse cross-section of travelers – from well-heeled superstars like Gwyneth Paltrow and Chris Martin to easygoing backpackers carrying a surfboard under their arm. Best of all, development is being carried out at a sustainable pace, ensuring the region will remain naturally beautiful. Here's a top 10 list to…