I think a careful analysis is necessary. Owing to my scholarly education at a tier 2 university, I am compelled to offer my humble opinion.
I think the author is trying to imply that even though he likes to have fun, he keeps it within limits. He believes that his heritage plays an important role in how much is allowed. "When heavy drinking is in the cards, I usually default as the “designated driver/bondsman” in case the crew ends up in trouble. " (pak-one, p. 1). Here the author clearly states that he is the more reasonable person of the group and an implication is made that he doesn’t drink.
But then the author states that he may not know if he might enjoy a drink or two, as he states when he says “But this time they weren’t sure about my plans, so they came well prepared.” (pak-one, p.1). It is clear that the author is not clear in his intentions if he should drink or not. Later on, we do see that the author does enjoy a “Tangerine Tonic” (pak-one, p.2), but that is the only drink he has the whole night. The author goes on to state that “…As the only Pakistani in the crew, the mates had always been understanding of my alcohol policy which allowed them to cut loose and drink with impunity.” (pak-one, p. 2). It is clear that the author decided to have only one drink and based that decision on his heritage.
Thus, in conclusion, the author appears to be level headed, who knows his limits, and can maintain control. He owes this partially to his Pakistan heritage.
EDIT: WHOA! My tier 2 education failed me. Tangerine Tonic is not alcoholic. So my mistake, I came to the wrong conclusion. Pak-one did not have any alcohol that night.