There is a cluster of restaurants around the launching point for Blue Grotto trips, and Step In is recommended for terrace views out to sea and over to the little island of Filfla. It's very informal, and the food and service can be mixed at best, but it is a good place for enjoying a drink with Mediterranean vistas.
The same owners operate a more informal cafe nearby and also a snack and drinks kiosk at nearby Ħaġar Qim.