I don't agree that it is "up to the officer" make a the final determination as to whether you are intoxicated. In GC 411.171 the definition of "intoxicated" is assigned to have the same meaning as it does for driving (PC 49.01).
The simple introduction of alcohol into your system begins the impair your mental or physical faculties. It may not end up with your being arrested, etc., but the possibility exists.Sec. 49.01. DEFINITIONS. In this chapter:
(2) "Intoxicated" means:
(A) not having the normal use of mental or physical faculties by reason of the introduction of alcohol, a controlled substance, a drug, a dangerous drug, a combination of two or more of those substances, or any other substance into the body; or
(B) having an alcohol concentration of 0.08 or more.
In the instructor school this summer, they hammered that (A) pretty well. I make sure students are aware of the fact that they don't have to blow .08 to get arrested for 'carrying while intoxicated'. From there, let your conscience be your guide.