Category Theory certainly isn't useless, and has some really beautiful and interesting things going on. One of the bigger issues it has is that it is relatively so young as a discipline within math. (Imagine what people said about set theory in 1910.) Your toughest hurdle as an undergraduate is finding a university that is offering it as an accessible class depending on your level of mathematical background. I haven't noticed a lot of universities even offering it at the graduate level yet either.
That being said, David Spivak's new book Category Theory for the Sciences which came out of MIT Press last year is the closest textbook I've seen to attempt making Category Theory easily accessible to not only an undergraduate audience, but also to a broader range of scientists who are not necessarily steeped in mathematics. For your particular purposes, it actually has a nice handful of biology related examples in the early chapters.
Because it expounds on some of the beauty of category theory and it's application to science, I'll draw your attention to an essay that Ilyas Khan wrote recently: https:/
I'd recommend category theory more highly, if you plan on pursuing a Ph.D. and research work, but in the meanwhile you might also find some interesting material in John Carlos Baez's Azimuth blog or on the n-Category Cafe.