I remember reading an article about the remaining few in the Statesman a year or so ago, but don't recall the town they highlighted. Nonetheless, a quick Internet search gave me a few results. One was a drive-in that may still be in use in Utopia, Texas. But, I couldn't find any more info as the link was dead. I did find a listing at The Link . I'd certainly call before going to any of these theaters. Very few left -- as you well know. The link for the San Antonio (current movies) was up and running (see The Link ).
Also found The Link -- pretty up to date!
According to this, there are more than a few still around in Texas, including ones in San Antonio and Shiner. The one in El Paso that shows X-rated movies only sounds a little scary, though. The Link