If Temecula historically has NOT had a 24-48 hour cancel policy, and for your dates it DOES, logic says something is going on in the area....
Also seems that if you wait, you may not get a room!

I would make the reservation.

When flight delays have prevented me from reaching my final destination, I have called CS and explained As long as I still showed for the remainder of the res (which I did), never an issue.

Of course, it also helps if (in your example) you stay at a Marriott property in DFW!