We wintered in Texas for a number of years and NEVER had any issues with NOT having reservations. Can't ALWAYS get into a specific campground or into a specific site but PLENTY of camping available in that region at least. We always enjoyed traveling without reservations because it left our schedule completely up to our own discretion.
Good luck / Skip
2011 F-150 HD Ecoboost 3.5 V6. 2550 payload, 17,100 GCVWR -
2004 F-150 HD (Traded after 80,000 towing miles)
2007 Rockwood 8314SS 34' travel trailer
US Govt survey shows three out of four people make up 75% of the total population