I've been using EF-S 17-85mm f4-5.6 IS for wedding shoots(portraits) ever since beginning of this year. I'll recommend it, although alot claim its not sharp, I feel its pretty acceptable. IS is a bonus! And range, after 1.6X crop is 28-136mm which is pretty much group shot to portrait.
the 70-200f2.8 as a good versatile telezoom, but i find that can be a bit of a pain aiming the 70-200 in close quarters in a portrait shoot (even with IS). would prefer using a 50mm or 85mm as a pure portrait lense.