In ST II Khan (Ricardo Montalban) makes a quote attributed to Klingons, even though he'd only been revived in the 23rd century for about 15 years and spent most of that time marooned on Ceti Alpha V. In a trek novel covering those years of isolation, it's revealed that McGivers informed him on the subject of the indigenous inhabitants of Kronos.
I think it would've been more interesting if Khan actually met some Klingons. Maybe if a small scout ship with only three crewmembers crash landed on Ceti Alpha V. Two would die in the crash and Khan and company would rescue the badly injured third one. As he was recuperating Khan would talk to him and eventually befriend him and learn much about Klingon culture. Probably a ceti eel would get to him, though. Which would explain his absence in ST II.
I was kind of surprised that there wasn't any encounter like that in the novel, though. I thought it would've made things more interesting than Khan hearing about Klingons second-hand from McGivers, as brilliant a historian as she was.