What constitues public intoxication? In a case where an officer stops a vehicle on a complaint that passengers were earlier causing a disturbance at a local convenience store. Officer asked an individual to exit the vehicle (back seat), found him to be intoxicated. legal public intoxication arrest or maybe not?

I think it's legal. See Ardis v. State, 05-00-01189-CR, 2001 WL 6783, (Tex.App.--Dallas,2001.
Jan. 3, 2001, pet. ref'd) (not published) (distinguishing public lewdness cases) ("The evidence showed appellant was in a vehicle that was being driven on a public road in "Deep Ellum," the "entertainment district" of downtown Dallas. When the vehicle was stopped, it pulled into a parking lot that was accessible to the public. The officer could reasonably conclude appellant was in a public place. See Chilman v. State, 22 S.W.3d 50, 56 (Tex.App.--Houston [14th Dist.] 2000, pet. ref'd); Peddicord v. State, 942 S.W.2d 100, 109 (Tex.App.--Amarillo 1997, no pet.); Jackson, 745 S.W.2d at 396. In any event, after the officer stopped the vehicle, appellant got out of the car and was, at that time, in a public place")