Most cameras have scene modes for landscape, portrait etc. Just read the manual. Cameras might be very advanced.. but none can read your mind to know what you think. You have to tell the camera by selecting a few things.
Ok so ya don't want to spend alot of time learning how to use the camera to the max. At least learn the basics and use av and tv modes and get used to using the dial to flip up and down and your holiday snaps will be sooo much better.
If you are going to just use auto the whole time then just use ur phone and leave the heavy gear at home.
There are some very good examples on the web if using point and shoot and focussing on the composition if you don't want to use the full creative capability of a dslr.
That is a funny question. It is your DSLR, it is your shooting style, you can use whatever mode you like and whatever mode you feel best for you. If you think auto mode would get you the best result, then by all means, use it. If you want more control, then use Tv mode and Av mode, or 'M' mode. If you are Canon user (not sure what other brands would call this mode), u can use 'P' mode too.
its all depend on you, if u know what ya doing you can use manual if you want, and if your not sure about what ya doing, just use auto mode and the camera will set the setting for you, all you need to do is to aim and shoot =D