Hi RosiS,
I mirror the sentiments of the other posters. As a first-timer to Trinidad I would not recommend driving alone. Very agressive drivers, poor road conditions, lack of adequate signage, crime. Also too sadly many of the tourist sites are not set up for tourists, no guide books, no signs, no guides etc. If you can find them, you basically go in and wonder around on your own.
A tour or taxi would be much safer and many drivers will provide at least some information on where you are going or what you are seeing.
There are many dining options on Ariapita Ave, pubs, wine bars, restaurants, street food, bars. featuring local and other foods such as Italian, sushi, korean, chinese. for clubbing recommend 51 degrees, Zen.
Trinidad is a great place to visit with very interesting food , culture and people.
if you are here I definitley encourage you to go over to Tobago for some beach fun for a couple of days. The beaches there are much more acessible and varied than Trinidad and the pace is at a much slower "Island life" speed. If you are into marine sports, Tobago has some great diving and snorkelling.
Hope this helps.