Earlier this year, the mayor of Guaynabo decided to start putting up traffic signs in English. According to the mayor, this is to help people familiarize themselves with the English, which also happens to be the island's other official language (in addition to Spanish, of course). Such a move caused quite a stir, as practically all the island's traffic signs are in Spanish. There are also political and socio-cultural aspects to this debate though. The mayor of Guaynabo is from the blue party (PNP) which is pro-statehood. By the same token, we've also seen other mayors from this party implement this measure. For example, Guayama has also decided to switch to English traffic signs.
Ironically, the Websites of both the municipality of Guaynabo and the Puerto Rican government are available in Spanish only. The local tax department (el departamento de hacienda), does have an English option though. Although English is also the official language of the island, Spanish is what people speak in Puerto Rico. Most schools on the island, especially not those in the public education system, do not introduce English into its curriculums until much later. However, those who attend some of the elite private schools on the island have a much higher chance of being introduced to the English language at a younger age. There are several of them which teach in English only.
Traveling throughout the island, the majority of traffic signs will not be in English. Oddly enough, in areas like Condado and Isla Verde, where tourists abound, I believe most traffic signs are still in Spanish. This makes no sense at all, consistent with so many other things on this island. In the meantime, for English-only speakers, here's a list which you might want to be learn:
"No entre"=do not enter
"Velocidad Maxima=Max. Speed
"Proxima Salida"=next exit
"Zona Escolar"=school zone
"Cambio"=change (you'll usually you'll see a "C" above certain pay tolls on the highways, this is the lane for those who do not have exact change)