I agree with you Cosmo. I also see alot of times, for people who are 1/2, where the "officials" (birth cert., etc) list you as your father's race.
I have several family members who are 1/2 PR and 1/2 AA and some of them ID more with the PR side and others with the AA side of their families. Like you said, I think what you ID with is a reflection of the culture, etc. of the person who raised you and the side of the family you were closest to.