Taking calculus will open doors and allow you to major, minor, or take upper-division or graduate courses in physics, math, chemistry, and engineering. With that said, only take calculus if you have the time and the desire to do well. You can get into medical school without it.
Calculus Made Easy by Silvanus P. Thompson was printed over a 100 years ago. It’s a great book. I basically used the Thompson book in place of my calculus textbook for the first 1.5 semesters of calculus. Because it was printed over 100 years ago, the copyright has run-out. It is legally and readily available on the internet:
http://en.wikipedia.org/wiki/Calculus_Made_Ea sy