It really depends on how far you are away from any given access point, and how many people are connected to that particular access point. The 802.11b is THE industrial standard for wireless ethernet, so that's probably what your school will do. We here at Dartmouth has got about 97% campus coverage since the initial installation back in April, and almost all the time it works great, that I could get coverabe anywhere I walk. The only problems we've had recently is oversaturated access points with too many students trying to use it.
Security is definitely a problem, even with the industrial standard EAP/LEAP 128-bit encryption. I can't say much about that since we haven't even turned on the encryption for our wireless yet because Apple hasn't released the encryption-enabled Airport card for the iBooks/PowerBooks (yes, Dartmouth has been a Mac campus, and they're dragging the rest of us down!).