YES YOU CAN!
I called the state Democratic Party Democratic Party of Texas
at 505 West 12th Street, Suite 200
Austin, Texas 78701
(512) 478-9800(512) 480-2500 (fax)
....and the wonderful person who answered the phone said that I can vote in either party primary by saying at the poll which primary I want to vote in (no declaration of loyalty is necessary!)
From Wikipedia: Texas - Semi-Open Primary (Mar 4) & Closed Caucus (begins Mar 4, schedule based on party rules). Voting in primary is prerequisite for caucusing at precinct convention, which convenes after primary polls close. Deadline (Feb 4, 2008).
An American Research Group poll shows Obama slightly ahead in Texas as of Feb. 13/14, with Obama at 48% and Clinton at 42%...
In terms of where independents are going, ARG reports that Texas independents comprise 22% of the electorate and are breaking 71% for Obama, 24% for Clinton. According to the Rasmussen Reports, Clinton currently leads among both White and Latino voters. Obama leads among African-American voters. ...