I'm a lot further East of your target area in Collin County.
In the Southlake and Keller area you have Lake Grapevine. I'm pretty sure there are some nice paths around there. The entire Southlake area is quite nice and supports an active lifestyle fairly well. I'm doing the Wounded Warrior ride on the 13th in Southlake.
It's not always blistering hot. Many times, overnight, we drop down into the 90's! Just kidding. The best way to describe the weather is we tend to treat the last half of June through mid to late September as the Northern folk tend to treat the dead of winter. The good thing is the early mornings are quite manageable, and once you are here for a transition of winter to spring, and have the chance to acclimate as the heat picks up, you do much better.
The really good thing is that you can ride year round for the most part. What we consider cold you will scoff at, lol.
You should also post over in the Texas forum. I think most of the DFW Clydes and Athenas tend to be more East of you, but there are plenty of Dallas area BF'ers. You have some LBS choices over your way that are reportedly pretty good as well.