Trig is big in mechanics, and really solid algebra skills will help you throughout. No one can tell you whether or not you should take a math class. I did. It had been a number of years since I had taken math, and it had always been my achilles heel. When I decided to do a post-bacc, I was going to have to wait until the next fall, so I basically had an open semester and took a precalc course. I found it extremely helpful, as I had just gone over all the math stuff in excruciating detail, so I could focus on the concepts and not deal with any kind of math refresher.
The way I look at it: precalc isn't a terribly difficult course, you've got a free semester, and it certainly won't hurt your prospects in physics to take it.