Puerto Rico is part of the U.S. postal system (USPS) and has the same mail rates (28Â¢ for a postcard, 44Â¢ for a first-class letter) and service as provided on the U.S. mainland. Post offices are located in every city and offer Express Mail next-day service to the U.S. mainland and Puerto Rico.here are different methods to find a job in Puerto Rico. Here are a few tips: 1  Ask for job leads from: family members, friends, people in the community, and staff at career centers. 2  Knock on the doors of any employers, factories, or offices that interest you, whether or not they have vacancies.