I want to display a map with the infowindow box automatically displayed for the single marker on the page, much like http://code.google.com/apis/maps/documentation/javascript/ex
You are mixing Javascript and Ruby together. Take a look at your javascript debugger (you are using one right? If not, the web inspector in Chrome or safari is great, as is Firebug for Firefox) and you'll see it complaining.
Without seeing your controller code I can't give you too many specifics, but take a look at this post and it might point you in the right direction.