Is knowing Spanish a legal requirement to work in Puerto Rico?

I personally know Spanish, but I'm just wondering, seeing how Puerto Rico is a US territory, and US citizens have the right to live and work there, could all-American Johnny who knows not a word of Spanish move there and get a job at McDonald's? If they refused to hire him for not knowing Spanish, would that be legal? I'm just wondering how language works as far as Puerto Rico goes. I know the natives all speak Spanish, but seeing as it's a US commonwealth and one of its two official languages is English, I'm just wondering if English speakers have any sort of "protected" status there. No smart-*** answers either; I want answers from people who have actual experience either living or working there. Another question; if I commit a crime in Puerto Rico (not that I would), would I have the right to a trial in English?