Looking for a budget accommodation for a night (on a whim), we stumbled on Residence Marine Hotel Diamant which surprised in the best ways. Pressed against time, we did very little research on the place, but rather stuck to the price - book online.
The staff was extremely friendly and also spoke English. The hotel was easy to find, but it is a little drive east from Diamant. This means if you want to go to the beach, you have to drive to the beach instead of walking. But they do have a very nice pool (with slide) and beautiful, unobstructed views of the sea, Diamond Rock, and St. Lucia in the distance.
We did not eat here, but the hotel basically the same menu that you'll find anywhere else on the island - pizza, fish, chicken, ice cream, etc.. The rooms come with a balcony kitchenette so if you want to pop into the Essomart at the roundabout, it's easy to prepare your own meals - it includes a fridge, microwave, plates, cups, stovetop, and silverware. Another great perk was the secure parking area they provide - which makes you sleep easier.
The room itself had air conditioning, a TV with very few channels all in French, and a little tired looking shower/bathroom. WiFi is also limited to the lobby only - which is kind of a drag. Nonetheless, we didn't mind it and it suited us perfectly for our needs and had a great night.