Need cable TV cabling help from under house

I'm no expert, but here's what I'd do with how homes are constructed here.  I assume you have some type of baseboard or molding?  Take that off in one section.  You can purchase a super-long drill bit.  Drill where the baseboard normally is at a slight angle down and toward the wall.  Hope it pops through eventually underneath.  Go underneath and find it.  Drill UP with your normal bit from there and you "should" be behind the wall cavity.

Or if you have an electrical outlet, either on the baseboard or the wall itself, you might try tracing the  wire from there.  You can shut the power off to an outlet, remove the cover from the outlet itself, and try fishing a wire down along side the outlet box and see where it comes out down below.  Once you've narrowed it down this way and also by observing the electrical wire location, you should be able to figure out where to locate your cable wire.