If I recently got a citation for theft and this will be my second charge, do you advise I get an attorney before I see the judge?

It is generally best to consult with one or two attorneys before you go to court on a criminal charge.  The value of more than one consult is that it gives you different perspectives about your case, your options, and the judge you will be appearing in front of.
Without know the facts of your case, the info that I can provide you will be a bit limited.. but this is what I can guide you through:
1.  Your new theft charge can potentially be enhanced by your old theft charge.  So... if you were looking at a class B misdemeanor... it could jump up to a class A misdemeanor with an enhancement.  Since you just received a 'citation', it sounds like they are only pressing misdemeanor charges--because felonies are charged via indictments, not 'citations.'
2.  Depending on the level of your offense, any other criminal history you may have, and what kind of mood the prosecutor is in-- you could be looking at a fine, a probation, or jail time up to one year in the county jail.  Texas does not have sentencing 'guidelines' like the feds do... so there is not an exact formula to tell you what the punishment will be.  An attorney can only tell you what it could be. 
3.  You do have the option to just show up, pay the fine, and go home.  Hundreds of people do this everyday because they don't think they can afford an attorney.  The problem is that you really should hire an attorney for certain offenses... and theft is one of them.  Many employers will refuse to hire you because of theft convictions... so even though you save a $1000 by not hiring an attorney, you could be depriving yourself of thousands more dollars in job opportunities. 
4.  As a general rule, the prosecutors in municipal and JP cases tend to focus more on fine collection than jail time.  This is not to say it won't happen... but it's not usually the biggest push.  So... you don't need to be stressing that you are looking at a twenty year prison sentence.
When you do visit with attorneys, here are some other things you should keep in mind and/or ask:
1.  Look for ones that offer a free or inexpensive consultation.  It's a good way to gather information about your jurisdiction.  It will take some leg work, but it will help you make a much more educated decision.
2.  When you visit with the attorney, do not hire the first one you meet with.  Visit with at least two attorneys before you make a decision.  This will give you a better feel of what you do or do not want in your representation.
3.  As you visit with the attorneys, ask what specifically know about the court or judge your case will be assigned to.  If they have never appeared before that judge... find a different attorney.  You don't need to be their test case.  Ask them what programs the court has available, like diversion programs.  Some court have limited programs where you can earn a dismissal via community service. 
4.  As you visit with the attorney, also look for ones that know the current expunction laws.  Even if you have to take a deferred sentence, you may be able to structure the plea deal in such a way where you can get an expunction or order of non-disclosure so that you can eventually get the case off of your record.  If the attorney doesn't understand expunction law, then they won't know how best to structure the deal.
The main thing is don't be afraid to ask questions.  This is your life... it's your case... find the attorney that understands your case and seems to grasp what can and should be done in your case.