Unless it's a dance cruise, the instructors will assume the students have not had any dance lessons before. The emphasis is generally to teach something today that the class can use tonight. On one cruise we took the instructors were dancers from the entertainment troupe. They did a good job, and even showed us a cute pattern in Merengue we hadn't seen before. A greater problem is finding a place to dance on the ship. Our worst experience was a cruise in which the room with the best dance floor had the worst band (except for one evening--and the response from the audience would have told the cruise people something if they had been watching). The best band was playing in the atrium, and people were doing their best to dance between tables and in the corridors. Unfortunately dancing is generally not a high priority with the cruise lines (who have to fit what they offer into limited space and time), even when they offer dance instruction.