http://www.washingtonpost.com/wp-dyn/content/article/2010/04/27/AR2010042705323.htmlYMMV.
Every day you don't fire your weapon will likely be better than the ones where you do. Every day you leave it concealed will likely be even better than either of those.
I'd consider all options, try to avoid it, make sure it was really menacing us, etc. before taking any action.
Consider the perspective of witnesses. If the coyote is five yards away, growling, and moving closer, take immediate action. If it's 100 yards away, standing still, and merely watching you, be aware and ready but don't engage. Somewhere in the middle will be up to your judgment.
If you draw OR shoot, call the police immediately.
Good luck!