Should I leave work early?

No

You should probably stay inside and do some work. It's obvious that you're insanely busy already or the weather sucks or you're incapable of being sneaksy.

Either ...

Pros: Finished all my work. Cons: I am the boss so people would notice.
Yes!

Why are you still reading this? Go outside, grab a beer and kick back. Sure, you may eventually get fired if you keep leaving in the middle of the day ...

Pros: letting the stressful work day go as i enjoy a little sunshine. Cons: not finishing everything i need to do, and having more ...