M.,
First: I really, really hate when someone who is not an early childhood specialist or therapist mentions autism to someone. That is a truly horrible thing to say and most people really don't know what they mention 'casually' can become a deep hurt very quickly. So, unless their own child is autistic or that's their line of work, I'd ignore that immediately.
Second: For 2.5 years I worked as the lead teacher off an older toddler group (20-30 months). It was very common for children to come into this group babbling and using only basic words. Most of them left that room quite a bit more verbal, and they all came to using verbal language at different times.
Good on you for not Googling autism or speech delays. In my opinion, you can often find more reasons to worry than not online.
Teaching some babysigns is a good idea. I'd start with the ones you think would most convey his basic needs to you. Another idea that works with bright children is to make a set of picture cards which your child can bring to you. This task will take a day or two, but can really help. Find pictures (online or in magazines) of things your son needs: to be picked up (pic of a parent holding a child), a cup of milk, a diaper change (pic of baby being changed), favorite foods, etc. You can cover them with clear contact paper instead of laminating. Then, you can put them together with either a big binder ring or using adhesive magnets (Office Depot/Max will have these) put them on the fridge. Every time you offer him something there's a card for, show him the picture on the card. Encourage him to show you with the cards what he wants.
Also encourage him to use a quieter voice, and lots of simple praise when he brings the card to you. "You showed me the banana! Thank you. Now I know you want the banana. Let's go get one." (Cheerful voice on your part.)
The signing or cards is not an overnight process. This may take your son a while to learn. Once he's getting the hang of it, you can remind him in simple language. "No scream. Show me the (card, sign) please." Then, show the child each card or sign until they can point it out. Overstressed and upset children will have a harder time focusing so outwardly, but being proactive and getting to the matter before they get completely upset will really help.
Lastly, two things: keep an eye out on media exposure. It has been proven that more tv time is a great contributor to expressive language delays. AND if you are still not seeing any more language acquisition in the next four or five months, then it is wise to check in with the pediatrician, just so it's documented. My experience, however, of all the children I've taken care of over the years, is that they do come to it eventually.