No cheat code exists to make homies follow you constantly in GTA IV (PS3). The game's companion system is scripted—homies (Little Jacob, Brucie, Packie, Dwayne) appear only during specific missions or activities (drinking, darts, shows, helicopter rides).
If You Want Persistent Followers: Play GTA V (Bodyguard CEO ability), Saints Row 2/3/4 (homies as gameplay), or GTA IV on PC with mods.