+1 on removing the wheel well splash guards.
There's a fastener on each side above the splash guard near the body that you can't reach unless you at least partially remove the splash guards. Also, you need to unplug the electrical feed to the fog lights before you drop the front bumper cover or you'll break something (take a guess how I know this). To unplug the fog lights you have to remove the splash guard. I just replaced the horn on my '07 and that front bumper is identical to the '05. BTW, there's only one horn, on the driver's side. Last piece of advice: have a blanket or a large piece of cardboard under the bumper cover so it doesn't get damaged. It tends to drop all at once with a thump.