You have to realize that wireless bandwidth is shared. You don't get 11Mbps per user, unless you're the only user on that particular channel. If you've got a lot of people trying to use the internet, and all of the wireless routers are trying to go through one 1.5mbps DSL line, it's going to be quite slow.
Also, if the internet cafe didn't design their WiFi network intelligently there are going to be a lot of collisions (I believe that's the correct term) because multiple access points may be trying to control the same channels. That drops network throughput significantly.
Thirdly, if there is even one Windows user on the network with an unpatched box... all the traffic generated by that worm/virus infected computer will bog things down horribly.
As a home user there will only be a few people on at a time, and you should see much better throughput. I've got a 802.11b network at home, and my daughter and I are both on it simultaneously quite often. It "feels" like I've got sole access to the cable modem - meaning the speeds are such where any slowdowns are at the other end (many/most Webservers are not going to provide your data fast enough to top out your DSL/cable pipe).
So anyway. Except for computer-to-computer large file transfers within your house, you're going to see the same performance from a wireless network as from a wired one. BTW if you have an 802.11b client on your network, your whole 802.11g network will be pulled down to 802.11b speeds.
) is for. Otherwise you will have to settle for the humdrum wired transfer speed of 100 Mbps.