I think you would be better off installing multiple AP through the areas. This will give you greater flexability. Can be used with your existing hardware/switchs. All will have problem with the concrete walls. You may need to set several up to provide good coverage. I have and use USR5450 AP, 11g. These are very good in range. Mine on low power will connect @125mbps after going through 4 walls and 55'. They come with High Gain antennas, a big plus. Most of the problem will be with the internal mini cards on LT. Most are junk. My internal has problems going through 2 wall with my AP on high. I use USR5410 PCMCI card, with internal off. I use mac and pc with mine, no problem. Some of the older macs had a restriction with the key length. The underlying problem would be bandwidth. The newer powerbooks play well with the USR AP.
This article will give you an idea of how different hw mfg plays with each others. And the reason I went with USR.