Blah blah hostel and lost hostel are good options. I have stayed there. there are couple of hotels on cliffs might be little costly. lost hostel and blah blah hostel is just near by cliff. u just have to take a turn.
A vacation during Mid April especially in Kerala not at all advisable since the weather will be too hot & humid. Now itself news paper reports are there that more than 300 people in a day are getting affected by Sunburn and dehydration. if you still prefer to go no need to book any hotels or hostels or resorts just walk in see the place and strike a deal. There are few other nice beaches and small islands which you can explore other than the cliff. Most of the restaurants near the cliff serve amazing food and drinks.
Would you prefer hostels or a proper resort by the beach side.
Varkala has both these options
I stayed at a resort by the beach and it was a decent one.
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