We stayed in Santa Maria on Sal in November 2015 in a small hotel Odjo d'Aqua right on the sea, but not All Inclusive. Lovely hotel with a good restaurant, they were building a lot of larger hotels/beach front resorts to the west of the town so that's probably what you are looking at. The weather was good from memory around 25C at that time.
Not much on the Island, it's pretty bare but there is an old Salt Mine further North and West of the airport for a trip out. As Giles says very friendly people and no hassle from the street traders, we liked Santa Maria town quaint with a number of nice restaurants.
