I've had grad students [Roman Catholic] studying in Greece.  They did attend Divine Liturgy and received Holy Communion. Many times,  no problem. But they also were pretty well acquainted with the Divine Liturgy of the Greek Orthodox.


That's the key---know what to expect when you go.  Not only is Communion received differently [very deep 'spoon'--for want of a better word], but one should be comfortable with their liturgical texts [written in modern Greek, of course] which are used extensively during Divine Liturgy.   Homilies/Sermons are in modern Greek also---so knowing some of the language is very helpful.


My "kids" dressed like the rest of the folks---and none of them were blond and blue-eyed---so they did fit in.