When exactly is housing day? I think I remember it being on June 11, but I'm not 100% sure. As for finding apartments in SF cheaper than the tower... I'm not so sure about that. It might be possible if you're hunting with roommates, but I'm looking for a studio or a place to live by myself. McAllister is by far the cheapest rate I've found so far. Keep in mind that basically all utilities are included at the Tower. You also get free wireless internet access.
If I don't get a space in McAllister, I'm probably going to look for housing in the East Bay. Rates are cheaper, plus I've found that places in the East tend to have parking included. I sent my deposit a few days ago for McAllister, so I expect to find out by the end of June.