I have to agree with hermione on this one. I am in PBL, and the one thing that most PBL, ISP, and LDP students agree on is that, in many cases, the lectures aren't worth a lot. Most profs just read directly off of a powerpoint.
If you are an independent learner, I strongly encourage you to wait to make your choice until after gross anatomy. All 3 pathways meet as a group during gross, so you'll meet lots of people. You also get a taste of the ISP pathway during those 12 weeks. It's plenty of time to make a decision. However, if you make your choice now, it's a pretty good bet that they won't let you switch back.
Good luck.