I know some people are more likely to get GI cancer than others. Which ones?

Many. Smokering, heavy alcohol intake, low fiber, high red meat intake and processed food, excessive caffeine intake, patients with family history of GI cancers, personal historey of inflammatory bowel disease, women with a history of breast cancer, are a few of the risk factors as well as age over 50.
Depends. There are many forms of "gi cancer." stomach cancers may be related to some smoked foods, excess alcohol use, cigarette smoking. Colon cancers may be related to high fat foods and hereditary family risks. Exercise, high fiber and low fat diet, and proper weight maintenance may help reduce intestinal cancer risks.