Echoing a bit of user1728 and Sean's comments, Category Theory is a wonderful unifying language that ties together a lot of ideas and makes certain things much easier, but it is pretty rough going to learn in the abstract.

I was lucky enough that the professor that taught Abstract Algebra at the National University in Mexico when I took it did a lot of the proofs as if they were category theory, but without actually *saying* "Category Theory". So he proved that the product of groups has the universal property of a product, and the uniqueness up to unique isomorphism, and so on, with diagrams; did the same thing with rings. Etc. By the end of the course, he was mentioning that all of these ideas were special cases of a general theory called "Category Theory". And so on.

By the time I got to an actual course *in* Category Theory, I had a whole library of mental examples to draw upon when looking at all the different concepts, amplified with some of the less algebraic-flavored examples (such as considering a partially ordered set as a category, etc) that the professor for that course gave. With that in hand, the first couple of chapters of Mac Lane's book became easier to digest and understand, and use elsewhere.

Of course, this may slant my view; I tend to view Category Theory more as a useful unifying language than as a particular subject (in which I am at least somewhat wrong, if not more). But I suspect you'll be able to get into, and get a lot more out of, Category Theory if you have the library of examples on hand.

Of course, as I said, I was lucky: I was primed for Category Theory with examples that were essentially Category Theory without saying so. You may not benefit from that. Still, I think that waiting until you study some abstract algebra and see some of these constructions in action might be a good idea.