1. My job will be in Guaynabo but I also really want to be in an area that is a close walk or taxi ride or near public transportation where I can enjoy nightlife, bars, restaraunts and the beach. Where is the best place to live?
All depends on your budget. If you can afford to spend $1000 or more on an appartment, you can go live in Condado or Old San Juan. That's where the action is (according to my 22 y/o daughter)
2. I am 33 and I enjoy hanging out with a 28-35 year old crowd, How is the nightlife scene for the 30 and up crew?
See #1.
I can't answer 3 and 4 - I'm getting old I guess..
5. What is the hottest time of the year and what is the coolest?
We're in the Northern hemisphere, so our 'summer' is in the same time as in the USA: July, August, September are the hottest months. That's also the time of the year for hurricanes by the way.
Here's an overview of the average temperatures throughout the year: http://www.topuertorico.org/reference/tempera.shtml
6. I have a Jeep Cherokee. Should I bring it or leave it?
I wouldn't take it. Transport and taxes here don't make it worth the while.
7. Should I bring my furniture (not very much just a bed, couch, small pub Table and TV) or is it cheaper to rent furnished apartment?
I wouldn't take my stuff. You can rent furnished, especially if you rent from private people.
8. I will likely be assigned to PR for atleast 2 years. What are fun weekend trips close to PR that I should take advantage of?
Close to PR there are Culebra and Vieques, two smaller islands that belong to PR. Also the Virgin Islands are a short plane ride away.
9. I have a passport and DC driver's license, can a live with that or will I need more?
Passport is fine - you won't even need it since PR is USA territory. You will have to get a PR license, either by taking the test or exchanging your DC license for a PR license at the DTOP.