Some sound advice above.
I would suggest not going on amn arranged viewing trip, it will tie you into one agency and they will dictate what you see, when you see it etc etc, if they are paying for your trip they will apply huge pressure constantly to you to buy, not the best way to vist Portugal and find a new home......avoid this type of pressure, just book a flight with a low cost airline, fly in, rent a car and explore, this way you can look at lots of different regions, speak to lots of different people and agents, this will give you a balanced view of what is available and at what price, rather than a carefully managed viewing trip where you have no freedom.
Its easy to rent a car here, easy to find a place to stay, so why not just do it that way, you will enjoy the trip more, have your free time and be allowed to choose where you want to visit and what property you want to look at.
If you speak with some agents by email before you go, they will advice on places to stay in thier regions, if you need help.
As far as all the does and donts of buying property here in Portugal, if you do your research, ask lots of questions, you will soon understand the buying process and will not be led astray by dodgy sellers.
take a look at the post about
Tips for home buyers, some good info for anyone thinking about moving to Portugal or buying property.
http://www.expatforum.com/expats/po...s-living-portugal/17054-tips-home-buyers.html
good luck with your plans.