Hi, and welcome! First, do read the site's Frequently Asked Questions and How To BookCross pages - you can find them under the "information" tab. Then browse the forums and see how people interact. The (Not So Random) Acts of BookCrossing Kindness form ( http://www.bookcrossing.com/---/10 ) is a good place to offer books; just make it clear whether you want to swap for other books or postage, or are happy to send books with no strings attached.
As for release zones, the "go hunting" pages can help you there. I don't see any OBCZs in Atlanta ( http://www.bookcrossing.com/---/104909 ), but there are lots of places where people have released books in the past, including several Little Free Libraries - a good place to start, if you aren't comfortable leaving books on park benches and the like just yet!
Another way to get acquainted is to look at the top of the page under Community and go down to click Forum where you'll find a list off all our Forums. Click Spanish-Espanol and introduce yourself in Spanish and invite other members to check out your Bookshelf. You might want to tell them that you'll do both Wild and Controlled Releases and that you'd be willing to trade books as well. If you want to send books through the mail let them know if you'd be willing to mail locally or internationally(can be expensive.) If you send books to destinations within the USA be sure to use Media Mail as it's often less expensive than standard mail.
It takes time to figure out how to best do things at BookCrossing but you'll figure them out one by one. Remember, we were all Newbies once.