The Hostel Zion Beach House is directly where the Kiteschool is, you can jump from your bed onto the board.
Bed in the big dorm (8 Beds) aprox. 17 USD
Bett in the small dorm (4 beds) aprox. 24 USD
Private room aprox. 70 USD
A 10min-walk away you can find the Hotel Aria and the Hostel Stamp.
If you don't want to miss out on the lively nightlife in Cartagena, you can choose one of the hundreds of hostels and hotels in Cartagena Centro Historico and head to the beach in the Pure Kite shuttle.
Here are a few tips from the young and active Getsemani district:
Casa Ebano *** (nice hotel, cheap and with warm water (rare) and Rooftoppool)
www.hostelmamallenacartagena.com * (hostel on the party strip Media Luna)