If swimming or staying under the sun are your goal, than Monte Gordo is a good option - the water is the warmest in Portugal, the beach, though generally crowded is large enough for the thousands that use it.
Lodging and catering are cheaper than in the top touristy destinations.
That's why the percentage of Portuguese people in this beach is much bigger than elsewhere, only the Spanish taking advantage of the proximity to mix with us.
There's not much to see and do, locally, but is possible to make a few short trips to some interesting points - Faro is less than one hour distant, and Seville less than two hours, for instance.
If you stay at the Monte Gordo area, you must go and see the beach called Praia Verde. It is much cleaner and nicer than the hotel area beaches, there are not so many tourists, also local people. The area is built to be beautiful. Praia Verde is just 2-3 kms away from Monte Gordo. In my second picture of this story you can see Monte Gordo (the wide and high houses on the left; picture taken from Praia Verde beach).
There is a very nice restaurant too so you don't have to stop your day at the beach for just searching for a place for having lunch or a drink or buying water. The restaurant does not look like a beach place; it has nice wooden furniture and a great menu. It is not one of the cheapest ones though.
In the restaurant you can sit either in the shadow of the palm trees or in the sunlight, according to your wish.