Just remember that you'll be using Rosetta as a backend for Word and Photoshop until their respective companies port them over to OSx86 proper. There will be some performance issues.

If you want portability you can't really go beyond a 14.1". A 15.4" notebook is possible to carry around comfortably, but they're difficult to place on the regular school desks. I can't really recommend any lower-end models, but look at HP if you want an alternative to Dell. Asus is also a great brand, but I don't know too much about their lower-end machines.

How much are you willing to spend?