I'm surprised your WRT54G hasn't let out it's magic smoke already.

Here's a randomly chosen cricket graph of one of our residential /25 subnets at berkeley. So, about 100 people, we do some light bandwidth controls at the building level, campus does some more when we hit the edge of campus depending on where the traffic is going. That subnet of approximately 100 people is averaging 5Mbits a second over the day, and we still get complaints about speed occasionally.

If you want this to work well in the long run, they need to be willing to pay for a fast connection, real routing hardware, and real traffic shaping hardware. It's not going to be cheap. In the outside world, people pay $20-40 a month for their home internet connection which usually serves at most 4 people. $10 a month times 150 residents, and you should be looking at spending 1.5k a month on the connection for residents pretty easily. The residents are probably paying close to a thousand dollars a month to live there, and the internet connection is probably in the top five things they care about right after electricity and food.