I had breakfast this morning in a restaurant that is planning to have musicians in on the evening of the 17th to play Irish music. (This is in St. Paul, Minnesota.) The hand-written announcement on their white-board called it a "St. Patty's Day" event.

I thought about calling the misspelling to their attention, or even correcting it myself if I could find a suitable marker, but the staff seemed busy and there was no marker in sight, so I let it go.

How bad is this mistake anyway? Is it worth mentioning?

I'm a regular customer there and I sort of feel that I have a stake in making the restaurant look good. Some of my friends have played there, including my wife.