you can find impala in much of Kenya - in any of the major game parks and even in the small ones. They are mostly in the savannah, so should be anywhere in the country that's not Mt. Kenya and other highly forested areas.
The impala lives in wide open plains in Africa, in herds of near a hundred.
Impala are among the dominant species in many savannas. They can adapt to different environment by being grazers in some areas and browsers in others. They graze when the grass is green and growing and browse at other times.