I Keneth, I´m from Portugal but I live in the North, which you are not going to visit.
You have to possible ways to get to the Algarve from Lisbon: follow the highway and you'll get there in less than two hours drive or follow the highway to Setubal, cross the river by ferry to Troia, follow the coast to Sines, Porto Covo, Ilha do Pessegueiro, Vila Nova de Mil Fontes, etc up to Sagres which is already Algarve and then go East through the coast and get to know all of the coast of Algarve.
I obviously would recomend you to follow the long route to the Algarve if your objective is to get to know Portugal well and take good pictures.
Go to my site:
www.pbase.com/mnogueira and see the gallery called "Porto Palafitico". It's near Troia. If you which to know more, please ask.
If you do this, you'll be going through "Costa Vicentina" which is part of a region called "Alentejo" and one of the most beautiful parts of Portugal. (much better than Algarve in terms of nature, in my humble opinion).
Also Sagres is the least "Turisty" part of Algarve (I haven't been there for some time, so I don't know how it is now) and, again, one of the most beautiful.
By the way, although I live in the North of Portugal, I currently work in the South, in Sines, so I am here during the week days. If by any chance you are thinking of driving through, just let me know. Who knows if we can't talk personally and I'll be able to help you a little bit more!