S.M.
My son was only saying 5 words at 2, so we had him evaluated through AZIP on the pediatricians recommendation. They were out within a couple of weeks for the evaluation, but the actual services didn't start until 2-3 months after that. The person that came out was nice, but I couldn't see that it was doing anything for my son. Luckily for us during this time, my son's vocabulary suddenly exploded. We were reassigned to a new speech therapist recently who reevaluated him. He is now in the normal range for his age, which is a HUGE improvement. That being said, we are going to keep him in the program and have him retested by the school district when he turns 3, just in case.
Personally, I found AZIP to be very slow and bureaucratic. However, I never really pushed them because I could see that my son was making so much progress on his own.
On a sidenote, have you considered teaching your son sign language? I did that, and I think that helped him quite a bit. That way, since he couldn't make his mouth say the word, he could still get his point across to me. Once he learned a sign, I would make him use it before I would respond. I used a book called Baby Signs, and also there are a couple of Baby Einstein DVD's that teach sign language (we have the one called Baby Wordsworth).
I know this was a long response, but I went through a lot of agony wondering why my little boy just would not talk. It turned out that he was just a late talker. All kids do things at their own pace, but it's always good to be proactive about it just in case.