IMHO, FS is far superior to st Regis. It is a much nicer beach and location. The Maya Riviera is far away 2-3 hour flight and you may have to connect through Mexico City so I would not recommend unless you have two weeks. Also keep in mind the weather in Mexico. It varies depending on where you are going, but Puerto Vallerta/Punta Mita can be quite hot, humid and rainy in Aug, Sept, and even Oct. best weather is usually dec-march although with weather changing everywhere it is not always predictable!