Epaulino4-
I saw your other post and decided to respond to you here. As for transport to/from the airport, I believe there are buses that run fairly regularly. I didn't use this option because they only run until about 11:30 at night and I didn't get in until after midnight. So, I took a taxi, which cost me, if I remember correctly, 14 euros (which was a flat rate). As for transport within Santiago, it's so small that you can walk everywhere, and in fact, in a large part of the old town, it is pedestrian only. There are buses that run within the city and to the outer parts of the city if you prefer to do that, but I think you'll find that walking is the best way to see Santiago. I didn't take any day trips, but you can easily get to La Coruña, Finisterre, and Pontevedra by train, bus, or car if you have one.
Enjoy your trip. Santiago is a wonderful city!