We stayed in this hotel recently. It is immediately next door to the Mangalares (nice hotel but more than 2x the price) The beach is the same. Flamingo has clean rooms, Sky cable TV, otherwise basic. Nice small pool overlooking the beach/ocean. Free beach loungers available, no restaurant. Get the end room by the pool & you may be able to take a midnight skinny dip if all is quiet. We did. In the off season most restaurants close early - by 7pm. There was only one which stayed open until 10 pm.
Be sure to take a boat tour of the area to see the flamingoes and mangroves. If you are a birder ask for Ismael at the government tour facility at the entrance to Clestun by the bridge.