I'm glad to hear youre interested in Engineering! Its a great field and you really can do whatever you want with an engineering background.
I don't know specifically if whatever school youre looking at has an engineering survey course, but almost all engineering schools do. Usually it would be Eng101. The best thing to do is look at the course catalog for whichever school youre interested in (usually online if you dig) or call their engineering department. My freshman year I started as an undecided in engineering, which put me into the engineering 101 class. 101 was a survey style course where each of the department heads from each engineering discipline came in and spoke to us about their program, what you can do with it, what to expect. We also took tours of the labs and did a few basic engineering projects which incorporated a variety of disciplines. Your best bet would be to check with the school. But Im 90% sure they will have an intro to engineering course for you to take!
Another idea would be to look at the websites for: ASME (mechanical engineering), AIAA (Aero Engineering), ASCE (Civil), IEEE (Electrical), AIChe (Chemical), BMES (Biomedical) and whatever else you can find to get a better feel for what each discipline does. And also remember some are cross-functional. I'm a mechanical engineer by degree working on airplanes, which is more Aerospace, but they have mechanical systems.
Jenn T Dandrea