You don't need to do baby signing if you are comfortable understanding your child however there are a great many benefits to using sign language with babies & young toddlers.
All children develop differently, on average babies get their motor control around 4-6 months (this is when they start to wave, clap & point, and aware they can control their own hands), the muscles in their mouth & throat don't strengthen up until around 12-18 months. Children don't get all their speech blocks until they are about 5 yrs old.
Signing really helps bridge the gaps: aiding babies who can't yet verbalise to use simple signs and gestures to communicate their needs / wants & observations. Support young toddlers & children who don't have all their speech blocks to clarify their spoken word and support their language development. Signs also act as hooks helping children to remember words and associate them with objects.
I started with my son at 8 weeks, just 'milk' & 'pain' by 12 weeks he was reacting to both sufficiently I could tell when he wanted his milk but also (and more importantly to me at the time) tell if it was teething pain or colic that was troubling him - he reacted differently for each - bliss!!!
I continued to use signs with regularly up until he was 3 and a half, as although he had an extensive vocabulary (over 500 words by the age of 2) as his speech was still developing some of his words sounded very similar so rather than constantly asking him to repeat words I didn't understand and knocking his confidence, I would ask him twice and then ask for the sign to clarify. This was much better for his confidence and a lot less frustrating for both of us.
I also found it very beneficial when I left him with anyone else (my mum / my brother etc) rather than spending 2 hours explaining all his little quirks, cries & mutters it was much easier to show them a handful of signs and have confidence that both they & he would be understood & understand.
THE MOST IMPORTANT THING TO REMEMBER IS TO SPEAK & SIGN AT THE SAME TIME. This way babies & children are exposed to spoken word too and you won't hinder their language development.
I enjoyed the class I took my son to , I certainly didn't find them full of competition and it?s not about being 'initiated' a vast majority of attendees are hearing adults & children however there are deaf adults & children too. Its all about making life easier for everyone - not putting barriers up.
It is also great for dual language families especially where individuals might only speak one language as the sign doesn't change whether you are speaking English, Polish, Russian, German etc.
You do need to use the signs at home as well as at sessions (if you don't they'll still pick it up it will just take longer) the more they see the quicker they'll recognise them and react to them (and in turn use them). It can feel a little awkward to start as you get used to using the signs however most people gesture to some degree when talking and you soon find yourself using the signs with ease and to everyone!
Try a local session, all groups are different and use different signing structures and incorporate different elements / different formats. So it?s worth asking them what they use and trying more than one if you can.