We were recommended this cafe/restaurant, and popped in on our last day.
There are vegan options (vegetable skewers with chips and salad) as well as lots of vegetarian options (omelettes, salads, etc.).
The menu is provided in English and Portuguese.
I ordered the vegetable omelette, which came with chips and salad, and was probably a 4+ egg spanish omelette. It was huge, and I didn't manage to finish it!
Would definitely recommend, as, for 14€ we had 2 drinks and two large meals, a lovely place to sit, and a chance to relax.