To a certain degree, yes. The five languages (don't forget the sixth major Romance language, Catalan-- the national language of Andorra) are closely related, but what's most important is the degree of lexical similarity.
However, it must be understood that they will not get by speaking their respective languages, and hoping that the others will understand. What would happen in a situation where the five are communicating with one another "for the sake of survival" would be the emergence of a crude pidgin, greatly facilitated by the fact that all five languages share broad swathes of their lexicon.
If you've ever been in a situation where you have had the need to communicate with someone who speaks English very poorly, then you know that a speaker, in order to be understood, will rifle through all of the words that he or she might know for a given object, until he or she hits upon a word that you understand. For example, the Romanian word for "heart" is "inimă", which a speaker of an Italo-Western language would not be able to readily identify (it probably comes from Latin "anima"). Of course, if the speaker needs to communicate something about his heart, he'll begin trying other words for the organ, or for related concepts, and he'll eventually hit upon "cordul", another Romanian word for "heart" that is reflected in other Romance languages.
As you've probably experienced, if you can understand one or two words in a sentence, you can often get the gist of its meaning. A higher level of communication would not be facilitated by the similarities in the grammar of the five languages, especially given the fact that they rely so heavily on inflection to project the meaning of a verb (in pidgins, and creoles alike, this type of inflection tends to get dropped immediately, in favor of simpler TAM markers).
Basic communication, enough to survive, would be achievable based on the level of mutual intelligibility between the languages. However, this is only the case because it facilitates the creation of an effective pidgin language-- to reiterate, the five will get nowhere trying to communicate in their own languages, but should be able to slap together a common medium of communication, if you will, rather quickly.