ROCK/POP Firefall: ''Break of Dawn.'' (Atlantic. 80017-1.) The country-rock sound of Firefall started in Denver seven years ago and has been plodding along ever since. Its new album is pleasant, though it doesn't include any major accomplishments. Subjects of the songs range from relationships beginning (''Fall for You'' and ''Falling in Love'') to relationships ending (''Take Me Back''). The Album's highlight is the cut ''it's Not Too Late'' -- a song with a hip beat, above-average harmonies, and well-written lyrics.