People should get married when they feel they are ready to get married no matter what stage of life they happen to be in. Being in college should have no bearing in the decision if the couple feels they are ready to be married and start their life together. Being in school is something that the couple has chosen to do and getting married is another choice they can make as a couple.
No, people should not get married while they are still in college, because young marriages don't often last. People who get married later in life are much more likely to stay married. In college, a person is still figuring out what they want in life. If they get married, they will likely change and then be disappointed that they got married so young.