Dear Sir,
Better to get down in Alwaye(Aluva) which is the closest railway station to Munnar and before Ernakulam also. You will get taxi as well as lot of private buses are running between Alluva & Munnar. It is a direct state Highway ie A.M. road (Aluva-Muunar Road). You can save at least 2 hours..
Best regards
JAYAN