Dean,

Puncture vine weevils are a good option in controlling puncture vine, however they are not the sole solution.  As you probably know the weevil feeds on the seed (goat head) thus preventing it from germinating. They do stop the seeds already in the ground from germinating and those plants from coming up.  Using weevils alone is a slow process.  It is good to use them in combination with a pre-emergent and post-emergent.  Also getting a good stand of grass will shade out the goat head weed and seeds and out compete the weed.  If the area you are talking about you are not able to water in a pre-emergent or get a good stand of grass the weevils along with a post-emergent herbicide will be your only option. Weevils are a good piece of the puzzle when controlling goat head weeds.  Let me know if you have any other questions.