In the book Jay and Carlos aren't shown together very often, at the end they join Mal and Evie for the quest.
During the coronation party ("Set It Off") Jay low-fives Carlos when he invites Jane onto the stage to dance with her just before Jay is dragged on the the stage by Audrey. The two are usually seen hanging around each other and interacting positively though they tend to get into fights throughout the film due to Jay's aggressive dominating thieving personality. The two fought with each other over eating candy in the limo and then Jay tried stealing a thing Carlos wanted. The two both enjoyed playing video games. The two also joined the Tourney team though Jay was far more successful due to the skills he acquired from thieving. However, after being taught by the coach that being a team meant working with each other, Jay insisted Carlos be included in the game and the two won.
Jay gets Carlos a new cell phone.