Hi Carlos —
Like you I recently went through the process of trying to find a breeder in Colorado. The ones that continually crop up are Five Peaks GSD, Rocky Mountain German Shepherds, and Adelhaus.
After researching for quite some time, I went with Five Peaks GSD and we have a deposit for a puppy from Roy & Olivia's litter due at the end of January. I've had really good interactions with Elaine from Five Peaks — she's extremely knowledgable and passionate about her dogs. Just today I called with a quick question and we ended up discussing vaccination recommendations and food for 45 minutes. What really sold us was how she focused on finding a litter that was most likely to fit our lifestyle and goals.
Everyone needs to make their own decision on this — it's a pretty personal choice — but I've been very happy with her to date and I know at least one other person on this board who has a puppy from her.
In the end, I don't think you can wrong with any of the three breeders I mentioned.