Disclose everything. Hide nothing.
Don't waste your time and money trying to get your record expunged... you will never get it completely cleaned up in a reasonable amount of time, and they will still find out somehow. Right now, there are private databases that have your record in there. The municipal courts get the expungement order, however, noone forces all the private companies with old info to purge their databases. Expungement is expensive and slow (Especially in TX)
Explain in writing that you have been walking the straight and narrow for a while, and that you have learned lessons from your past actions... There is a part of the security application that gives you a whole page to explain.... you can attach more paper if you need to.
Also, think twice while you are at the bar... can you really afford to have this next drink? What if you get pulled over? What if they arrest you? That HAS TO BE DISCLOSED.
Think three times when you are at the bar, or at the movies, or at a concert... can you really afford to beat the guy's ass who is staring at your girlfriend? You may win the fight, but if arrested, you will have to DISCLOSE... EVEN IF YOU ARE NOT CHARGED!
You have to figure out what's important in life. One moment of trying to be the man, one little slip-up, and you are DISCLOSING.
I've had to check myself, and it's hard at first... how bad do you want to get the job? How bad do you want to keep the job?
Good luck.