You've already gotten some good advice already. Should you transfer? Maybe, but before you do, are you sure you really have taken full advantage of what your school has offered? You say you spent a semester in one of the upper level graphic design classes and saw how "awful" they were. Awful in what way...the quality the teaching, the available equipment, the assignments, your fellow students...please remember that a large part of being successful in any educational environment is often your response and energy to what is being taught. Ok, so maybe the assignment was a little lame, but how can your response to it still highlight your creativity and art skills?
You also might want to think about....What do other programs have that yours is lacking? Are you being realistic about your expectations of your school and of other schools? Are you prepared for the debt that a private college or university will incur....remember graphic design careers don't start out (or even end up) with high salaries. Also, it seems that, socially, you have become comfortable at your present school, would you be as happy and comfortable at another one? Coming into a new school as a Junior transfer can be difficult in some schools, as many friendships are often cemented during the first two years.
Also, I'm confused as to why you don't have a portfolio....you've been there for 4 semesters, which I'm thinking would mean at least 4 art classes, and nothing to show? Yes, for students like you, portfolios can matter in transferring, and will matter in seeking jobs or internships , so you might want to evaluate yourself and your efforts so far. How are your grades in your art classes? Sometimes when you have mentally checked out of a situation, it's easy to just stop trying. Try to avoid falling into that trap; grades matter and don't come with an explanation (as in "my teacher was a bozo") on the transcript.
Finally, if you do decide to transfer, be "professional" about it, no band-mouthing your former school. This could come back to haunt you; it is a small world out there in many respects. The phrase "It didn't work out for me" goes along way.
If you do decide to stay, talk to your teachers...tell them that you don't feel the assignments (or whatever) are working for you. Try to be diplomatic but specific. Most teachers, really any teacher, would be open to listening to a student's needs.
Best wishes on making this important choice. I apologize if I do not sound supportive, but this is a tough decision and I want to advise you to consider all the angles. If you have a faculty advisor, talk to him or her about your transfer ideas. If your school has any kind of counseling services, you might also want to talk to them too.