If you don't need it, don't bring it. After 50 dives I realized I hadn't used it once. Still one day when I had forgotten it, I felt my heart rush. Now what should I do??! Could I dive without it? But we used them in my OW and AOW classes! Well, I did my dive without it, and haven't used a snorkel to anything but skin diving ever since.
To use a snorkel in the surface, what's it good for? It's very much more straining to breath in than you regualtor. In fact, I am not sure you should use a snorkel during a "heavy" workout, as it can be to get back to shore in swelling seas.