Richard (aka "Mary's Son") provides us with an example of two logical fallacies in one (source):
Richard writes: "You can say Roman all you want to try to confuse the term Catholic; but go out on any street in the world and ask for directions to the nearest Catholic church: you're not going to end up in a Presbyterian church or any other church but in the only Catholic church there is; that which is in communion with the bishop of Rome."
1) The argument from ignorance. Paraphrased as: "Since most people don't know the difference between the term "catholic" and "Catholic," it must mean there is no difference!" The fact that most people are ignorant of the difference is a negative judgment on their education: it is not a way to establish the matter logically.
2) The argument from the masses. Paraphrased as: "If practically everyone thinks it is so, they must be right." The fact that most people think something is so doesn't make it true. Democracy is not the way we establish truth.
The refutation to this silliness is simple: Ask the man on the street for an "Orthodox" church, and he won't point you to a church in communion with Rome! Oh no. He'll point you to a church more or less loosely affiliated with Constantinople. It must mean (by analogous reasoning to that of Richard) that Rome, while "catholic" nevertheless has fallen into heresy! This is obviously unacceptable to most of those who would have the same church affiliation as Richard.
In fact, despite many bad arguments from "Orthodox" folks, I think I've never heard such an obviously bad one. It's too bad that there are at least some few people who think that the argument is a good one as applied to Catholicism.
Of course, Richard's underlying accusation, i.e. that people use "Roman" to try to "confuse the term Catholic," is a misplaced accusation. No one (that I've ever heard of) uses that term to try to confuse, but rather to try to avoid ambiguity, since there is a real and important difference between the church of Rome, which calls herself the "Catholic Church" and the universal ("catholic") church of Christ (all those people who believe on Him for salvation as he is offered in the Gospel).
Finally, it's not an horribly original argument. It's loosely based on similar arguments either presented by or attributed to church fathers. It's important to remember that not every argument made by the church fathers was a good argument. But when one engages in taking an argument about nomenclature, ripping it out of its context, and plopping into a new context a thousand years later, one should be unsurprised that it flops around like a fish out of water -- and just as quickly expires.
To answer the subject question, the catholic church is the body of all believers. It is not at an address: it is throughout the whole world. Its faith is preserved in all those churches where the Gospel is preached and believed. Thus, through metonymy, a "catholic church" (i.e. a congregation that fits the label "catholic") is a place where the faith of the catholic church is taught. By that definition, one would not look to the churches in communion with Rome, but in Evangelical churches.
Thus, if you get the subject question, I hope you'll consider answering: "Are you looking for a place where the Gospel is proclaimed?" And then directing them to such a place, or explaining why that ought to be their objective.