Your background is bright because the camera used a slow shutter speed to expose the car. And since there are lights in the background those lights were over exposed.
In order to get a nice looking background with a correctly exposed subject (the car), you need some sort of alternative lighting. And since this is outdoors and in a remote location the only thing that would probably work is speed light(s).
I see your shooting with an XTi, so yea speed lights is definitly an options. You can go with a canon 430ex or bigger 580exII. Or go with a used speed light, such as vivitar 280's etc, older canons, or even Nikon flashes.
One speed light might really be pushing it, but im sure you could make it work. but ideally a 2-3 light setup would kick ass for a shot like this.
Honestly my recommendation, find a new location...
Good luck man, and if your into photography.. Take the time to learn your hobby. check out these sites.
http://photography-on-the.net/forum/
www.digital-photography-school.com/blog
and for lighting
www.strobist.blogspot.com/
And hey, if you want to see some strobist style car lighting check out this flickr Pool.
http://www.flickr.com/groups/carstrobist/
I'm no pro, but i dont mind helping.