Hi,
'Fraid I can't help with Praia da Luz - have eaten at the Fortaleza some years ago but have seen mixed reports on it since then.
As far as Lagos is concerned, your choice is almost endless.Among our personal favourites are O Galeao,our favourite restaurant in the whole world,let alone Lagos, O Navegador- a three storey restaurant with sensational views over the Bay of Lagos from the roof terrace and A Vaca- a Swiss restaurant in the town centre of Lagos.
You could do worse than consult http://www.simplylagos.com.We have eaten at many of the restaurants featured on their website and their reviews are fairly accurate ( can't understand why O Galeao doesn't feature and still haven't got round to asking them !! )Don't worry, you'll have no trouble at all in finding the perfect spot for a special dinner.

Thank you for your reply I will have a look at that site.

I had a meal at Forteleza a couple of weeks ago and it was lovely. On the outskirts of Praia da Luz on the road to Burgau is a lovely restaurant called Brancazul which I highly reccommend. As it is so much bigger there is more choice in Lagos where it is also cheaper, due to competition. Wherever you go have a nice meal.