With only a few weeks, you cannot hope to understand how to use a DSLR to its full advantage. With an important trip, you do not want to screw up your photos trying to learn how to use it...you should probably use it in auto mode, or perhaps program mode, and letting the camera make the exposure decisions.

As far as the choices are concerned, you are basically limited to each manufacturers least expensive offering, unless you look towards older discontinued models. They are all pretty good; none is far and away better than the others. You should choose mostly based on how it feels in your hands, how you feel about the view through the viewfinder, and how the controls are positioned and/or accessed.