Tropical hideaways do exist on the island, but they are not the easiest places to get to. They require hiking through some tall grass, known as sword grass, but when you get there it is totally worth it. I will try and post some photos of the tropical side of the island. If you like to dive then Micronesia is the place to come. You mentioned Palau. I haven't been there personally, but I keep hearing rave reviews about the location and the people there.
I would be careful about airline prices. It is extremely expensive to get here and expensive to travel between the islands. United is the only airline that flies out here and they make the prices pretty high. And you will have a hard time finding flights online to any of the islands, because they only fly certain days of the week. If you don't get the exact days right, they will tell you that there are no flights on that day and ask you to start your search again. They won't tell you what days they fly to what island.
Hope that helps.
I think last year I did a quick check of those prices and even with a sort of airpass it was indeed extremely expensive, especially to visit the islands that make up Micronesia itself, and the Marshall Islands as well if I am correct. '
I could however find deals around €900 (about $1,200) from Amsterdam to Guam with Korean Air, which is not to bad. And from Guam it's an easy hop to the main Mariana island I guess. Palau is already a bit more expensive.
I am not a diver, but I do snorkel.. And I have the disease called 'island fever': I really like to visit islands. Unfortunately it is expensive indeed in many cases, especially the remote ones.
Is there a time to avoid Guam etc, regarding crowds mainly (don't care about rain or so)?