Hi. As a parent with a child who was speech delayed, I just want to say advise you to take a deep breath, and calm down, because you are doing the right thing. Have your child evaluated, to determine if he is speech delayed. You will also have his hearing checked to determine if there is any hearing loss. Hearing loss is often a big factor in speech delay.
We, too, were a bilingual home, but once speech therapy began, the second language was put to the side. We do not really know why there was a speech delay, maybe it was confusion between the 2 languages (?). Now, at 7, my child is doing great in school and is relearning the second language.
Regarding autism, I have two first cousins whose children are autistic. The one characteristic that was common in them at about 18 months was the inability to intereact with others. It sounds like your little boy interacts and plays with others. However, you are your child's best advocate and should feel comfortable in the steps you need to take to ensure your child's healthy well-being.
Have your son evaluated, and if all he needs is speech therapy, that's great. And, if in a few months, you are still concerned, have him evaluated again. I happen to live in an area where there is tremendous state and local support and services for children, so we had a wonderful experience. At first, I was not satisfied with my child's speech therapist. We switched after several months, and the new therapist worked well with my child.
Good luck, and just remember you are taking the right steps. Often, the evaluation process may take several weeks, so keep this mind.
Regards,
J.