As Liza pointed out.. usually you will find that different clubs cater to different people. A lot really depends on the people who are running the club and their screening process.
For instance, the club that used to operate up here was very picky about only having "pretty" people. Something I didn't really care for.. simply because the hosts ideas of "pretty" people lended itself more to stuck up people than to those with good personalities/attitudes about their looks.
If you look through the club listings here on the Swingers Board and read the reviews for the various clubs you will see that some of the clubs tend more towards upper-class attractive swingers and others in the opposite direction.
Swinging is a cross-section of society, but the people you will find at any particular club might not be. If looks are all you are worried about then you should contact the club and ask them if you can meet in advance with some of the couples who attend. This should give you a good idea of what to expect from THAT club. However, it will not give you an idea of what to expect from every club.
Julie
http://www.swingersboard.com