In lieu of a post-bac program, why don't you look at taking non-credit classes: at a university, residency-type place like Ox-Bow, or a local community art center? That way you can bulk up your portfolio, find an artistic community, and continue your education as an artist, without shelling out as much money as you would for a post-bac. I never stopped taking art classes after I completed my undergraduate degree. I can tell you that the 3 classes I took at Ox-Bow over the course of several summers provided the springboard for my MFA application portfolio. Now I'm in my 30s and about to go to the school I fantasized about as an undergrad.