Jack
My ranking of those that I have played:
1. Vilamoura Old - a must play but make sure you take your handicap certificate or you won't get on. Very old-fashioned and understated. Tree-lined but plenty of room. Great variety of holes e.g. par 4s range from 290 to 450 yards in length. Marshalls also do a great job in ensuring a good pace of play.
2. Vilasol - a Donald Steel design. Has 27 holes but make sure you get to play 1-18 as 19-27 not that great. Very tough opening hole. The stretch through 4-7 (par3, short par 4, par 5, par 3 over water) is excellent.
3. Quinta Do Lago North/South. The South course is slightly better. Wouldn't normally recommend getting a cart but courses is quite hilly and some long walks between tees (between 8 and 9 on the North for example). Both very enjoyable.
4. Pinhal (Vilamoura) - front 9 better than back but a solid course. Not really a 'must play'.
5. Millennium/Laguna. Course on same site and share a clubhouse. Cheaper that the rest. I like Millennium but hate Laguna - too much water and not normally in great condition.
Never played San Lorenzo but hope to play it next time I go. Heard it is probably the best but with a price to match.
Victoria is, again, meant to be good but expensive.
I have heard mixed reviews of the Vale do Lobo 36 most of which are that they are not worth the money they charge. Plus, if you tee-off before a certain time they make you hire a buggy.
There are plenty of booking agents that offer green fess that are less than those advertised by the clubs (e.g.
http://linksgolfportugal.com/linksgolfportugal/golfprices.asp).