There are forums out there for GTA 5. This page has a list of some of the most popular forums currently on the web for GTA 5.
Here’s the list:
There aren’t a whole lot of forums as of right now because the game hasn’t been released yet. For most fans these forums will do, as they have quite a bit of activity, especially the first two.
As for playing the game, fans will just have to wait until the official release date in order to play the game.
Check out the "suggested by the author" links below for more GTA 5 information.