The 24-70 lens will be good for you. I can't spring for one either, too much $$ for me. But from what I have read it is an outstanding lens.
I had a Tamron 28-75 lens for a while that was great for portraits. I really liked it a lot but traded it for something with image stabilization for my old and shaky hands. You can pick up used copies for $230 and up. The lens I have now the Canon 28-135 IS is a good all around lens and works fine for portraits. You can find them for $195 used and up, and it has Image Stabilization which is a big plus. I had that 50 1.8 for a while and didn't really care for it, but a lot of people really love that lens for portraits.