You will often hear less used with plural countable nouns in informal spoken situations, but traditionally it is not considered to be correct:
We’ve got less pizzas than we need. There’s ten people and only eight pizzas. (traditionally correct usage: fewer pizzas)
And a good blog post on the topic that actually fits to this situation
He goes on to point out what less/fewer purists often ignore: that even countables may, in a given context, be considered as quantities rather than numbers. "For instance: 'Not many of these buildings are fewer than thirty years old.’ The thought here is not of individual years but of a period of time; therefore, less."