I think Loma Linda only offers Bachelor's degrees in things like Nursing, etc. It doesn't have an undergrad program in things like Biology or Chemistry. Most Seventh Day Adventists who enter Loma Linda Medical School are from schools such as La Sierra University and Pacific Union College (California), Southern University (Tennesse), all affiliated with the church.
There IS a preference for church members, but they do accept non-members as well for the medical school. Loma Linda itself is a very boring city in my opinion (I went there many times), and is basically dead on Saturdays (Sabbath for Seventh Day Adventist). However, it has a fairly large Asian population (Chinese, Filipinos, etc.)