I'm not really sure that there is an IDEAL age to get married...I think it has more to do with the individual person.  Take me for instance...

I graduated from high school in 1987.  I spent the first few years working at the same high school job and having a great time.  I was good at what I did, and actually liked what I was doing.  Then there was something that was eating away at me - just a nagging in the back of my head really - that said that there was more out there.  By this time, I was living with a man and his two girls (but no talk of marriage).  So, in 1994, I quit my job, found a different one, and enrolled in college.  I met a whole new crowd of people just by doing those 3 things in my life - all three very difficult for someone not really accustomed to a lot of change in her life so far.  I left the guy I was living with in 1997, and took my life in a totally different direction.  I was truly on my own for the first time.  I changed jobs again (more of a necessity this time as he was "dating" one of my customers!), and moved to a new city.  I met my husband in 1998 and we've been together ever since.

My point is this...I needed to have those experiences on my own.  I graduated college (only one in my immediate family to do that) and have found many things that I love to do and am good at doing.  I didn't get married until I was 30 years old - but I personally would not have been ready before that for the awesome commitment and work that it takes to make a marriage a true union of two hearts.  My husband and I are soulmates.  If I hadn't of made the decisions I did, and had the experiences that I had, I can honestly say we probably wouldn't have met, or we would not still be together.

My brother, my Irish twin, got married practically right out of high school to a girl he got pregnant.  They've been happily married for 17 years. 

So, after my rambling, it all comes down to this - each individual needs to grow in their own way and in their own time.  There is no ideal, stereotypical age for someone to get married.  Some people are ready at 18, some at 30, and some never are (or will be).