The first rule of the subjunctive is that English doesn't have one ... so don't use it. (This is a lie but it is close to the truth)
But English used to have a subjunctive and it is still sometimes seen in subordinate clauses.
I advise he use the indicative
"Use" is in the subjunctive.
But this isn't the situation in your example. The verb is not in a clause subordinated by the verb "advise" but appears in a content clause. Note the recipient of the advice in the example above is "he", the subject of the subjunctive verb. In your example the subject of "be" is "it" but the recipient is "would-be tourists".
It is therefore a grammar error to use "be". The verb must be in the indicative form "is".
You may (rarely) see a subjunctive. You never need to use it, and most native speakers don't use subjective much at all.
I advise he uses the indicative.