Many health clubs offer aerobics classes, but they may be quite crowded, so you'll need to take note of when the classes are held and may even need to make an appointment to ensure a place. Most aerobics classes are frequented by women, but men are usually welcome if they're serious.
It takes a good bit of confidence and willpower to continue at a health club for more than a few months. Be careful before you sign up for a year's membership; your club won't tell you that most folks rarely make it past three months. Go with a shorter-term option, if you can find one.