What I'm planning to do for my trip in September is split the park in halves, east and west, to visit over two days. One day for Soarin, Living with the Land, Nemo, Figment, etc., and then head up through Canada, U.K., France, Morocco, etc. Then head back that same way, or take one of the friendship boats from the "top" of the world showcase back to Future World (supposedly walking is faster). On the other day, do Test Track, Mission: Space, Sum of All Thrills, etc., and then head up through Norway, China, Germany, and so on.
This is how Josh on EasyWDW most recommends visiting the parks, and he's usually spot on.
http://www.easywdw.com/cheatsheets/ep_cheatsheet_v3.pdf
This method allows you to still have a mix of Future World/rides with plenty of time to explore World Showcase. I'm sure you can have fun doing it the other way, though, depending on how you like to tour the park.
I've never stayed in one of the Epcot resorts and entered via the International Gate, but I can't imagine taking a bus to HS, then a boat across the lake, and entering would be faster or less of a hassle than taking the bus directly to the main gate and walking across Future World. I'm sure someone else can answer better about that though.