Well there's a huge difference between those areas ... and the highlands compared to the coast. I suggest you make trips both winter and summer to see the differences for yourself. Since you are including Vallarta and the coast, I'd suggest you come down thru Colima and head north along the coast. Hate to have you miss some of the nice little places like Melaque/Barra, La Manzanilla and maybe even Colima of Manzanillo.