When choosing a viewpoint for photographing landscapes with people, pay special attention to the position of the sun. Often, the photographer's shadow will creep into the photo unnoticed. If you choose to shoot in early morning or in the late afternoon, you're likely to catch your shadow in the shot because shadows are elongated at those times during the day.
Often, you can take a great picture with people on holidays. Many people gather at beautiful landscape sites on holidays. If you choose to capture the event, it's best to stand at the entrance to the event. Position yourself above the crowd by standing on a large rock or stool. Make sure the people don't block the focal points or points of interest in the landscape. However, you can use this to your advantage as well. If there happens to be an unsightly object in the picture, you can use the people to block it out.