By "beater," most people aren't necessarily talking about walmart and kmart bicycles. An old, used bike shop bike, when well maintained, is not a theft magnet and may be quite fun and comfortable for daily rides. you should check out some of the old road bike conversions on the fixed gear gallery. www.fixedgeargallery.com I haven't put mine up there yet, but I have a mid-eighties schwinn with butted chromo steel tubing that I've converted with a rack and fenders. nobody would steal it (around here at least), I clean it and work on it constantly, it feels great... You don't necessarily have to ride fixed gear, but an old road bike might just be the ticket for you.

I agree with the others that you should extend your route to make it safer. I don't agree with you that you're too good for a beater. I also think that you have the right and responsibility to ride safely in the roadway.