For some of them, you can select the emission power. It's possible on the Linksys WRT54G if you install the DD-WRT firmware (I guess other firmwares for the WRT54G can do this too)."
You should try installing a directional Helix antenna. it's rather easy to build your self and cheap too. Mostly you can forget about connectors included and just solder it, although dimensions and coiling should be followed as accurately as possible for the antenna to work fluently. There are sites to be found with instructions how to. It's a directional antenna so it should be pointed at a hotspot. You can use a software eg. WirelessMon to help You with the right direction.
