What should I do?

I currently hold a b.s. in business management but want to make the cross over to graphic design. Maybe even working in advertising or public relations design. I work at a media agency so i do understand the industry. My problem is I don’t have training in design and IM thinking of going back to school. I don’t know if I should go for a certificate program to get my foot in the door or a traditional college program. I know going the traditional route is prob. better but I don’t think I have the energy to go through 3 to 4 more years of school that’s not for a masters degree. Advice anyone???