I live in Guadalupe County. I was arrested for Public Intoxication at my house & taken to Comal County jail. Is that a good defense at trial?

You were taken to the facility that had room for you - that's the way it works in NY.

No, you have to be charged in the county where the crime happened.

It does not matter where they arrested you,

It does not matter where you are being housed.
( often some jails are full and you may be held in many other places)

Lets say you were publicly drunk down town, but got away from the police, they find you a few hours latter in another city or state, they can arrest you there, Then you would be housed at a facility that is ordered by the arresting department.

But you will have to be charged where the crime happened and that is where court will be