I saw a few Bluebonnet blooms along the highways last week but the full effect is in the eastern part of Texas near Ennis. The chamber of commerce there gives out rural road maps for the best viewing. If you go, take picnic and plenty of water. You won't want to give up and sunshine to drive into town. Oh, and take a camera!
Here is what I saw north of Dallas along Highway 287. Not quite as far along as the eastern part of the state, but pretty.