Some universities have requirements, and some colleges/schools (within the university) have even more requirements. When I started at UWM, the College of Engineering and Applied Science did require 4 years of science to be admitted, but since it wasn't a requirement at my high school one of the CEAS advisors signed off on it.
I would call the admissions office of the universities you want to apply to in order to find out what their requirements are. UWM is pretty lenient as far as admissions, but I know other schools that are much more strict.
