I am not to familiar with the George Squared program. From looking at their website it seems as if it is a graduate certificate program. So I am not sure if the courses taken in the program count as post-bacc or graduate courses. If they fall under the "graduate" category on the AMCAS then it would be better to do a DIY post-bacc.
From what I've seen on SDN it doesn't really matter where you do your post-bacc just that you do well. The good side of the George Squared program is that they provide you with the Kaplan MCAT prep course which might be helpful. On the flip side if you did a DIY program and it was significantly cheaper then you could probably pay for the Kaplan course with the money you'd save anyways.
Whatever program you are considering, make sure that the courses you take qualify as post-bacc when you apply to medical school and not graduate courses. As per the most recent report from the AAMC, when considering who to invite to interview, postbacc coursework falls under the "Highest Importance" rating, while graduate or professional program falls under the "Lowest Importance" rating.
@toinfinityandbeyonce maybe be able to tell you if the courses fall under post-bacc or graduate.
