I had one experience at open mic night and never again...
It was advertised as an open mic but when I showed up the "house band" told me I wasn't playing. They were regulars who discouraged newcomers.
I left at half time, cried in the parking lot hugging my instrument then warned every music instructor I knew not to send their students there.
It closed up soon afterwards.
Nope, no open mic for me.
...Deb