Well late last night I spent about half an hour typing up info for this but now see it didn't make it here. Hmm. Anyway, again I say the Comfort and the Alamo are probably the top 2 choices of the 5 IMO.
The Alamo is at Hwy 46 and I-10, at exit 607 I believe. This means the track is 10 miles further W at exit 597, Santa clara Rd.
The Comfort is at Hwy 123 and I-10, about 2-3 miles E of the Alamo. It's a bit bigger than the Alamo, 3 stories I believe.
For you DFW folks, as you come down from San Marcos on hwy 123 southbound, towards I-10 and Seguin you'll find that the hwy makes a fork into Hwy 123 (L) and Hwy 123 Business (R) in front of a Motorola plant on the RHS. This occurs about 1-2 miles from I-10. Either fork will take you straight to I-10, so no worries if you don't figure them out in time

However The R fork is about 2-3 miles shorter to RCR than the L. But the Comfort is along the L fork. The Alamo is about 1-2 miles W of where the R fork comes out to I-10. Basically if you want to take the R fork bear right in front of the Motorola plant. This all occurs a few miles S of passing through the tiny burg of Geronimo.
Also, be careful taking the exit off I-35 for Hwy 123 S towards Seguin. It's exit 204A BTW. It makes a pretty tight bend onto the frontage road and would be a handful at high speed with a trailer. Don't take it fast.
TurboTR