Wow, I'm a similar weight and I've never broken a spoke. But I have a real hard time with the bike shops. I think they see an overweight woman, and they just don't want to help you or they have stereotypes about what kind of riding you're going to do.

I first rode a Bianchi Brava (loved it), but I got hit by a car and the bike frame was totaled. I now ride a Litespeed Capella and recently bought a comfort bike for commuting next spring.

My advice to you is to not worry about the brand but go in and try to find something you can ride comfortably to work as well as on weekends.