Usually with circle means able to communicate in the language indicated with shop or selected girl. Triangle is may be able to communicate in English with shop or selected girl. X means unable to communicate in the language indicated with shop or selected girl.
Yup, you see it everywhere, not just on Erolin and not just in the hobby in Japan. In fact, the japanese words for 'circle' and 'x-mark', Maru and Batsu respectively, are used colloquially in Japanese to mean good/correct and bad/no good.