The fact that you're asking the question indicates you may be best off by starting with a 50mm f/1.4.
I got this lens myself when I bought my 20D in the Fall and the 24-105 was backordered. I figured it would be a good one to have regardless, and I could sell it easily for nearly what I paid for it.
That was a good decision. I've used it a bunch (also have a 70-200 f/2.
, and I am enjoying the lack of zoom - forces me to visualize my shots even better.
The problem with wide angles for newbies is that they use them. :-) Learn to shoot tight first. Then discover what a wider view would do for you. Going the other direction is, in my view, more difficult (and less likely).