Ralieghs are reasonable starter bikes. They hold up pretty well and don't kill the purse so if you decide you don't like it, you're not out alot until you can sell it.
Cannondales are higher but are more suitable for the more serious minded. You can get just about anything you want with a Cannondale.
Stay away from the ones we remember as kids, Shwinn (sp?) etc. lol Been too many years since I had to spell that one.
If you are going offroad, automatically look into the wheels designed for it. Both of the above have good stock wheels but dirt paths will wear them out, so if you opt for the more expensive wheel to start you'll save in the long run.
If you decide on a model of Cannondale, let me know, and we can price it thru a friend of ours Bike Shop. He sales short...

I mean he sells all over the country to the larger name racers and gives pretty good prices even when you add the shipping.
