YES!!!! First you need to have his hearing checked. It needs to be checked in a sound proof room - not at the pediatricians office. If he has an ENT, they usually have "real" hearing testing equipment. In addition to having his hearing tested (which should happen first). Oh - before I go on - I have a son with a hearing problem and another with a speech problem so I am pretty versed and passionate about this topic!
Anyway - the hearing test is your first priority. Second, the state of Florida has a program that they fund for speech problems. The program is run, in Tampa, by USF. For the younger ages (under 3) I think it is called Fiddlers. The number you can call is ###-###-####. This is the referral department adn I always dealt with a lady by the name of Agnes. They will get you in the system. You will have to meet with them and answer questions regarding your child (at which time they will ask if his hearing has been tested and request the results), they will then schedule a meeting with you and your child/grandchild to evaluate him. They evaluate everything to see if he is developmentally on track as well as speech so that they can determine if he needs assistance (which it sounds like he might).
From experience, don't let it go on too long. The older they are when they try to correct the problem(s) the harder it gets. My 4 year old is just now saying things correctly and learning how to sound letters correctly. Can you imagine what would happen if he could not make the right sounds next year when he is learning to read in Pre-K?
Good luck to you and your grandson! He may just be delayed in speaking, but better to know that there isn't a problem then push it off and try to correct it later.