I would just enroll in the state school undergrad program and knock out the rest of your prerequs. The utility of a formal post-bacc is really pretty limited, in my opinion. Might be worth considering for people who haven't completed any of their prerequisites and need to take them all. Even then, I don't see much benefit over just enrolling as an undergraduate and taking the necessary courses.
Don't worry about the fact that you're not planning on finishing the degree. Just enroll and take the classes you need.