The gang members appear only during the mission Running Dog. CJ and Big Smoke go to East Los Santos and meet the two. They engage in a short conversation during which the Vagos insult Smoke, which prompts him to beat one member up with a baseball bat while CJ chases and kills the other member.
Like Big Poppa and Freddy, they use a generic Vagos model. Big Smoke calls one member Jose, although he was most likely just being derogatory, as "Jose" is a common Spanish name.