Welcome to the Forum, southernstars.
I did a bit of research on laying my boat up for the summer in Trinidad three years ago, but ended up in St. Davids, Grenada, instead. I wasn't too keen on Trini after talking with a number of folks who'd taken their boats there. If you've decided on Chaguaramas, you'd better get your reservation set. They fill up quickly. The most popular boatyards there are Powerboats, Peakes, and IMS.
Here's a thread that includes some discussion of southern Caribbean boatyards that might help:
http://www.cruisersforum.com/forums/f19/southeastern-caribbean-safety-24152.html
As to routes from Miami, do you intend to sail directly there, or island hop?