Hi nycjules!
I can only tell you about the west coast of PR so I will try an answer some of your questions concerning Puerto del Sol.
1- the best sources for current events are all of the publications that circulate in the area, We have a great one here in Rincon called "el coqui" that is free and loaded with information. I am sure each region has a similar publication which you can find in all of the local coffee shops and most definitely hotel lobbies.
2- As far as ride shares, all I know for sure is that most of the towns here on the west coast have trolleys that run from one side of the town to the other and several taxi services that are very reasonably priced that will drive groups around to different "tourist attractions" and beaches. If you are planning on moving to PR, I would suggest buying a car, there really is no cheaper way to get around the island.
3- Art festivals are again going to be listed in local publications. You can also check for fliers posted in coffee shops. The Patron Saint's Festivals are always held in the pueblo of each town. You can find the listed online.
4- Metting people can be tricky, as with any move, but if you don't speak Spanish it's a little more difficult here. You will find that Puerto Rican's are very friendly people and will sit and talk with you for hours and are not put off in anyway by someone striking up conversation. The beaches are a great way to meet people...Sunday's are family/party day and you will be able to meet and mingle with a lot of genuine, outgoing people...brush up on your Spanish.
5- Not sure what you mean about "negotiating life." Do you mean finding your favorite stores? Reliable contractors? A job? If your more specific, I'm sure someone on the forum can help.
6- Classes are abundant. It just depends on what you are interested in. Check local galleries for art classes and ask at the farm markets about cooking classes. If you can't find one you like, try placing an ad or posting a flyer asking for a dance instructor, cook, surfer, artist, etc., that is interested in giving classes. I get Spanish lessons from a college girl that works at the panadoria (bakery)...I suppose the answer is, "just ask around."
I hope some of this helps. As I said, it's really just a matter of asking around once you get here.
Good Luck!