The answer that deals with the reality of the question is simply-- no. If you are a hobbiest, getting a headful of polyester fumes won't hurt you. It might give you a headache, but no real injury will be the result. The MSDS makes reference to "chronic, repeated over-exposure" that may or may not lead to the problems listed. Hobbiests don't need to worry about this as their exposure is perhaps a few hours at a time. You'd have to work in a fiberglass shop, like making boat hulls, to get the exposure that could cause a problem. Even then, you'd have to define what 'over-exposure' means to understand what the MSDS is really talking about. This is akin to the result that doomed saccarine for so long-- mice were given massive doses over a long period of time and the result was they got cancer. The equivalent dose for humans would be such that you'd have to live on the stuff to get that kind of exposure.
Additionally, pertinent to the Bondo question is the question of exposure to acetone. It would be very uncomfortable, but you could take a bath in acetone and it would not harm you. Acetone is made inside our bodies and is expelled in our waste. Washing something off our skin with acetone is perfectly safe. The smell might get to you, but that's about all the danger that's involved. A chemist once told me that even exposure to ammonia is nothing to worry about. He said you could get into a situation where the ammonia fumes might make you pass out, but that's because the ammonia was so much a percentage of the air that you weren't getting enough oxygen. Even at that, its not really hurting you, though it can burn the lungs. As long as someone pulls you back into the good air, so you don't suffocate, no damage would be done.
Now, I know this has nothing to do with Bondo, but it does go to show that breathing the fumes of commonly available chemicals may be uncomfortable, but as long as you don't do something stupid (like glue sniffers do), then you'll be fine. Just use adequate ventilation to keep the fumes from getting strong enough to bother you.
And before someone takes me to task on this, yes-- I've discussed all of this with doctors. I used all this stuff, and more, for years in the movie business and the information was something we were all concerned with. And please note, this only addresses breathing the fumes or, in the case of actone, getting it on your skin.
Scott