Anybody else see signs asking for driver's license?

All voters who registered to vote in Texas must provide a Texas driver's license number or personal identification number issued by the Texas Department of Public Safety. If you do not have such a number, then you must state that fact and provide the last four digits of your social security number. If you do not have a social security number, you must also state that fact.

http://www.votexas.org/rights.html
HEY, YOU HAVE RIGHTS!

As a registered voter in Texas, you have the right to:

1. A ballot with written instructions on how to cast the ballot.
2. Cast your vote in secret and free from intimidation.
3. Receive up to two more ballots if you make a mistake while marking the ballot.
4. Ask the polling place official for instructions on how to cast the ballot (but not for suggestions on how to vote).
5. Bring an interpreter to assist you as you qualify to vote if you do not understand the English language.
6. Help to cast your ballot if you cannot write, see the ballot, or understand the language in which it is written.
7. Bring written materials into the voting booth to assist you as you cast your ballot.
8. Report a possible voting rights abuse to the Secretary of State (1.800.252.8683) or to your local election official.
9. Cast a provisional ballot if your name does not appear on the list of registered voters or you do not have proper identification.
10. Vote once at any early voting location during the early voting period within the territory conducting the election.
11. File an administrative complaint with the Secretary of State concerning violations of federal and state voting procedures.

Texas SOS FAQ
What if I don't have a driver's license, personal identification number, OR a social security number? Can I still register to vote in Texas?

Even if you have not been issued any of three identification numbers requested on the application, you are still eligible to register to vote, but you will be required to provide proof of your identity. You may enclose a copy of identification with your voter registration application, or you may present identification when you vote. Acceptable identification includes:

• a driver's license or personal identification card issued to the person by the Department of Public Safety or a similar document issued to the person by an agency of another state, regardless of whether the license or card has expired;
  
• a form of identification containing the person's photograph that establishes the person's identity;
  
• a birth certificate or other document confirming birth that is admissible in a court of law and establishes the person's identity;
  
• United States citizenship papers issued to the person;
  
• a United States passport issued to the person;
  
• official mail addressed to the person by name from a governmental entity;
  
• a copy of a current utility bill, bank statement, government check, paycheck, or other government document that shows the name and address of the voter; or
  
• any other form of identification prescribed by the Secretary of State.