Are there that many younger users out there (im 20)? If not, no big deal, as long as the older folk make me feel welcome on the air.
One of the big concerns in ham radio these days is that the average age of licensed amateur radio operators seems to be increasing. I'm not sure if our ranks are aging any faster than the general population, though. The ham radio club I used to be a member of had 1 member under age 30 out of about 25 members, if that's any indication.
Whether or not you are made to feel welcome on the air depends somewhat on you. If you get your license and just key up and start talking, you may be shunned by some of the older hams. It will serve you well if you listen to the local repeaters to get a feel for the kinds of people who hang out on them and learn the way things are done in your area. It will also help if you find an elmer. Not only will an elmer teach you things about ham radio that you will never learn from the test study guides, but they will also help you get your foot in the door with the local ham radio community.
Soon after I got my license, I was talking on the air with a guy who had been licensed about 20 years. He was quite surprised to find out that I was a new ham and complimented me on my on-air presence. I chalk that up to listening to that particular repeater for about a year before I got my license.
Luckily, you live near a large city, so there are probably a few different groups to choose from. Find out where and when the local clubs meet and attend a few meetings. Stop by Universal Radio out on the east side of Columbus as they probably know about local clubs or have flyers for local events.
Also, I've been reading several ham sites on the web and they mention how some repeaters are private as opposed to open. How do I know whether or not I may use it without getting chewed out on the air?
Closed repeaters are usually listed as such in the repeater directories. Here is a link to the Ohio repeater council's directory:
http://www.oarc.com/ORD_08_09.pdf I think I see one closed repeater listed in Franklin County. In this part of the country, closed repeaters are much less common than in other areas...like California.