People from the Republic of China (i.e., Taiwan) with English language proficiency don't refer to themselves as 'island China' or 'the real China' (barring fringe elements), but may call themselves (ethnically) Chinese. Generally though, they call their country Taiwan and themselves Taiwanese in English.

Besides, if ambiguity is the concern for people from the PRC, the phrase "I am from the People's Republic of China" lacks any political subtext.