I am completing my senior year at a Community College, taking most of my classes with an emphasis on Computer Science. I plan to leave with a “Certificate of Achievement in CS”; however, I will not have three years of lab science if I do this. (I will have four years of Math and English, though). So, how important is doing four years of lab science for admissions? My previous three years were Bio, Chem, and AP Physics 1 (5). Should I try to take another physics course over the summer?
Depends upon what colleges you are applying and their Lab science requirements. Having Biology/Chemistry and Physics is fine for the majority of schools in the US.
Not all CS majors at 4-year colleges require non-CS science, but for those that do, calculus-based physics (the version for physics and engineering majors) is the type of non-CS science that is most likely to fulfill or help fulfill such a requirement. So if you want to take an additional science, taking such a physics course at the community college is the one most likely to be useful to you as a CS major.
For college admissions, three years of high school science that are biology, chemistry, and physics is fine for most colleges, but some of the most selective colleges would like to see a fourth year that is one of those at an advanced level.