Pomona doesn’t have the level of public transportation like San Francisco or San Diego. Your only choices that actually come to campus are the MTA and the Foothill Transit Buses. However, the bus systems in Pomona are not exactly known for being on time.
Students can also take the train, which they can catch from the Pomona or Claremont depots. However, you would need a ride just to get to the train! In addition, there are no movie theaters, grocery stores, or shopping centers within walking distance. The closest grocery store to Cal Poly is at least a 10-minute drive, which would make walking there impossible. Besides, would you want to walk back carrying all those bags?
Biking is another option, but again, the distance and bags would still pose a problem. Without a car, you will be stuck with whatever food and supplies happen to be sold on campus at the Pony Express or the Bronco Bookstore as your only choices, unless your roomie has a car. And it will make weekends repetitive after a while. Bottom line: if you attend Cal Poly Pomona, you will need a car.