Ken
Bus info by line and route. Links suitable for mobile phones.
The best coverage in West seattle right now is actually AT&T/Cingular. The merger a while back created overlapping zones in much of WS and allows my phone to work in a basement of a plaster and lathe house (otherwise known as a faraday cage)when verizon users have to go out to the front yard.
Each location is going to be different, but since cingular built towers and then merged with AT&T which already had lots of towers, the coverage is better in most places I have tested. (poking around in cell phone software can tell ya some esotheric and interesting things about signal strength and inrange towers.)
However, the concentration of users on the afternoon West Seattle Bridge will often overwhelm the towers between Pigeon Point/Delridge way and the Alaska Junction.