I commuted for a bit from Katy to Greenway plaza on a DR650. I wouldn't recommend it unless you were willing to avoid the freeway.
In the HOV lane, I was able to keep up a speed that was reasonable relative to the flow of traffic, but it really felt like I was wringing my poor bikes neck. The KLR may be better at this being water coolled, but I think the Wee as recommended above, or an SV650, Versys, or Ninja 650R would all be great choices for this type of commute.
However, I would caution against jumping right in there a fighting rush hour on 45 being a new rider and all. He should take his time and build up to that. Take the BRC, get a license, practice for a while in parking lots, riding with a friend leading (at a slower than usual pace) on surface streets and rural roads, and do some off-road practice if he ends up with a dual sport. When riding in that kind of traffic there really is no substitute for being able to control your bike very well when it comes to avoiding the cagers out there. Good luck and enjoy.