Re: Aggie here, visiting Columbia next week
Hunter Gatherer is a brewery on Main St close to campus. They have good food and beer. My personal favorite restaurant in Columbia is Cantina 76, and they just opened a new one on Main St too.
Usually your best bet is call and set up a cab during the day. In the more populated bar areas at night (Vista and Five Points) you can usually walk up to one or flag one down.