Didn't care for Varkala that much when I was there 6/09. Beach is poor for swimming and suffers from too many local male lookie-loos. Layout of the cliff top is odd - massive parking lot/helipad the "promenade" itself is crammed on the cliff (some bits falling away) with some ok eateries (note - alcohol prohibited in the municipality though they'll give you a warm bug and a beer in a paper bag) and fantastic sunset views.
I'd suggest Sri Lanka. Generally more enjoyable beach experience.