I'm taking organic chemistry and physiology at the same time and I'd say taking two science courses isn't that bad. Oddly enough organic chemistry is my favorite class. I don't have a job or kids either and I use the bulk of my time studying. I think you can definitely handle it. Stay focused! However, if you do feel overwhelmed and feel as though you can't handle it, don't be afraid to drop one of the two courses or one of your GE courses. You never want to overload, if you have problems don't hesitate to talk to an advisor for advice, especially if your worried about finishing your pre-reqs by a certain time. It's best to take a fair amount of classes and get all A's as opposed to overloading and putting your grades at risk. Other than that, I say go for it and feel it out, if having both classes doesn't feel right then drop one before the drop-deadline. If you feel confident though, I say stick with it ! As long as you study and attend class you should be fine , GOOD LUCK !!