Op, def not, go for it. Yes, you will be behind most others but so is everyone when they start.
I would be careful in your choosing though, most are shit against anyone who knows how to fight, and only works vs people of the same style, or retards.
I have compteded in wrestling ni boxing via hs and college, and also trained in BJJ, Mauy Thai, tae kwon do, and a couple others.
If you are sticking to one, I would recommend, bar none, either BJJ or Mauy Thai. BJJ is not much striking, but lots of submissions, and has proven better than any other martial art via the UFC, esp when it first started and everyone was 1 or 2 styles, rather than the diverse sport mma has evolved into. BJJ is fun as hell too.
If you want to become great at striking, Maui Thai is the way to go.
Stay a way from your more conventional martial arts though, just saying. My one roommate in college was a national champ(not exaggerating)... Before, I even started training mma, I was only a boxer/wrestler, I dodged a kick and knocked him out cold in about 6 seconds. This was before I was even a good boxer.