The best one I know is Figueira which is between Lagos and Sagres.
Free excellent wi fi
Disregard the website as prices are wrong and the place is much better than it looks.
6€ night, if you want showers they are 1€ for 3 minutes.
Electricity is 25 cents per kw, and it costs the owner 23 cents per kw. It worked out at under 30€ for a one month summer stay!
If you stay for one month, the price is 5€ night.
Very secure, gates locked at night and lots of dog walking places.
We know quite a few people, including ourselves, who just went to stop a few days, and ended up staying for weeks and even months! That says it all!
Just search
oh, it only holds 38 vans