Dinosaur Valley is a great park...one of my favorites for hiking. We have not actually backpacked there, but have been by some of the camping sites while day hiking. Do be aware that you must ford the Paluxy River to get to the hiking/backpacking/mountain bike trails. That is rarely a problem unless there have been serious rains. Many people just wade through the water since it is not deep at the trail crossing. I did not want to get my hiking boots that wet. I have always used the stepping stones and rock hopped across with the aid of my hiking pole and not had a problem despite the fact that I am not very spry.
BTW, if you have the opportunity, notice that there are a large number of trails on the large map near the parking area that are not on the paper map handed out at the gate or
on the web. This unpublicized northern part of the park is higher in altitude and has some spectacular views that are not seen by many park visitors.