It's possible, but the level of knowledge would have been extremely limited. Most people who could write were able to write certain things, such as their names or business-related items, but it would have nowhere near remotely qualified as "literacy" by the modern definition. Literacy varied (obviously) by social status, region, and, most of all, profession. Clergy were the most likely to be literate, as has pretty much been the case for all of the Middle Ages. We tend to romanticize an era that was truly very different- although, in some ways, less backward- than we envision it to be. The printing press made its debut when Gutenberg did his thing around ~1440, but vernacular literature hadn't really hit the streets quite yet, and books were still ridiculously expensive. So yeah, short answer is it pretty much depends on your profession and where you lived. David Mitch's Education and Skill of the British Labor Force transcribes data from parish registers in England, and estimates literacy based on the rate of couples who were able to sign their name at the time of marriage. He estimates literacy in England at the time to be around 40% max for men and 25% for women, with numbers significantly lower near the 1500s (he has a chart estimating illiteracy at the time to be almost at 100%). Again, that's hardly a quantifiable estimate and wouldn't apply across regional/class boundaries, but, as with anything in medieval history, it's very difficult to pull statistics from a relatively under-documented population. Most statistics from the era are really just informed historical guesses. And, obviously, Romeo and Juliet was set in Italy. My guess would be, given the time period, it's possible, but unlikely, and if so, it would have been limited. I don't know much about Italy at the time. That's my very un-historical answer, but hope that helps.