[hvkumar]

Madurai route is better when coming from Trivandrum. The construction work on NH7 between Nagercoil and Madurai is not disruptive and you can make good speeds. Take NH7 all the way to Madurai where you do not have to go into the city. Continue on NH7 till Dindigul where you turn left into the road to Kodaikanal/Periakulam/Theni (I don't think Palani is marked on the sign boards. At Sembatti which is approximately 15-20 kms after turning off NH7, turn right and go via Othanchatram to Palani.

If you want to go on the Pollachi route (maybe a good idea for the return journey), go via Udmalaipet, Pollachi. At Pollachi town, turn left (straight goes to Coimbatore) and go to Palakkad via Gopalapuram and Kanjikode. Once you are in Palakkad (town is bypassed), you are on NH47 all the way to Trivandrum via Trissur, Kochi, Alapuzha and Kollam.