I send text messages constantly and expect a prompt response back from anyone I send a message to. When he or she doesn’t respond I just think it’s rude. What does God think about those people?

This is more of a question of etiquette and personal taste than of religion or ethics!  Some people are more tethered to their techno-gadgets than others.  Some don’t want to be reachable every single moment.  And some are just unable to respond right away; maybe they’re actually busy, or on a plane, or in a dead zone.  Given the variety of ways people use technology, your expectations are unreasonable.

While the teachings of the church don’t offer much in a direct way here, think about it this way:  when you pray and God doesn’t respond immediately—at least in a way you understand or recognize—are you just as impatient?  Or when God sends you some sign and you don’t respond immediately, does God dismiss you so quickly?  Try cultivating with others the same sort of patience God may show you.