If you are on a newer server (>=55), then the drop rate for medals is only 1%. Forget everything you've read in the those wonderful guides about farming medals -- those are for the older servers.
The way to earn medals is to attack lvl 8-10 valleys. I have earned every medal from Cross to Nation (except Wisdom) by doing this. I prefer attacking lvl 10 valleys, but I did earn a Rose from a lvl 8.
"I am the terror that flaps in the night! I am the stink bug that smears your windshield. I am Lightfoot Duck!"