As a fellow cyclist and former Assignment Manager of a TV news station I think I can help you out on this one.
Your letter has some great points but when approaching a news station you need to think visually and what you can offer them.
Is there some kind of advocacy group that is planning an event in your area, some big ride you can plug this off of or is there some kind of ride-along you can offer to them.

Unfortunately they are not going to seek you out until something awful happens such as someone gets hit by on a bike or an accident happens. This is just the way news works. I know it stinks...kind of why I don't do it anymore.

A great approach you can take is pitching it to a "Morning" Program in your area as a "live" segment. I know in many areas May is promoted as "Bike to Work" Month. If you plugged it along with something like that where you could have a morning anchor acutally ride to work in the morning. Have fun with it and pitch it as educational. I think they would be more open to doing something if it was visual, fun and informative.

You could chapperone them to work and explain the "rules of the road" and other things peope driving in cars don't think of. If they don't do it live offer it up to them in the form of a package. They would follow you and do a 1-3 minute complete story that they could air along with a possible live.

Follow up your e-mail with a phone call and take it from there. Get a name of someone on the Assignment Desk who is in charge of booking stories for the program you are looking to get something aired on. Ask for an anchor/reporter by name, get their e-mail and have at it! Keep calling...trust me we got phone calls 24/7, e-mails galore and are listening to police scanners all the time. Be short and to the point and offer up the things I listed above and hopefully they will bite!
Good luck and keep us posted. If you have any questions please let me know!