Hello lilygirl,
I felt compelled to write you immediately since you are expressing a lot of anguish! I hope some parents who have felt similarly to you will also write on your post.
As an SLP, I NEVER feel that parents own blame for their children not talking as expected at their age. Children come into this world "wired" the way they are, and parents are not responsible for that. When children are not hitting the speech and language milestones, it is NOT because of what the parents have or have not done. It just reflects on what the child's system has been able to do so far.
You have taken a very positive step--you got your son evaluated and into an early intervention program around 26 months. You are trying to get his hearing tested (why not call the center where you will be going and ask them to call you if they get a cancellation so you can get this completed as soon as possible to ease your worry.)
To answer your question, when children are behind in their speech and/or language development, and they seem to be developing in a "typical" manner in other developmental areas, I am always hopeful for those children that with specific intervention (in therapy and throughout the day in natural interactions) that they will acquire the desired skills to understand and speak. "Delay" in speech-language skills does NOT mean that a child has mental retardation. Ask your SLP to talk with you about your son's strengths in play, use of gestures to communicate, or other signs of his cognitive abilities. Also, a "label" applied to a young child does NOT have to be permanent.
I feel it is important for parents to read and learn a lot of information about what they can do with their children all day long to promote improved speech and language skills. Ask your SLP if she has not given you such information. I have written a lot of posts on the site, and you can search for them and read them here. And I have written a complete e-book for parents who are seeking a lot of information on the subject. You may want to consider reading it if you want to learn a lot of techniques you can use throughout the day.
I hope your son's successes start to ease your feelings of self-blame--soon!
Best wishes,
Mary Lou
Mary Lou B. Johnson, M.S.,CCC-SLP
http://www.helpyourchildspeak.com