Here are some infos about how to get your Social Security Number is your an "Alien" Expat. Obtaining a social security number will be your first step.
Find out more on work visas, work permits, working holiday visas and residence permits allowing you to live and work in Puerto Rico.
Basic information about work VISAs. You will have to pass through some process to get a L Visa type which will grant you the right to work in PR.