Our open mics are all predominately music open mic nights. Whereas we do allow other performance types, bear in mind the audience isn't used to non-music acts. That could be a blessing or a curse, depending on how engaging your act is and the audience that night!
As a side note for all performers; if your act is quiet, or really needs the attention of the audience (e.g. comedy, spoken word, poetry, some styles of music, etc) be prepared that the audience may not be quiet and therefore people may not be able to hear you properly!