I taught my daughter about 100 words of ASL (English with and ASL lexicon, to be honest about it). Turned out super useful since she was a late talker (my second child, who I also tried to teach ASL was an early talker and thought ASL was stupid).

In my opinion, it's mostly useful because it's super cute. Typically kids who can sign 'milk' or 'more' can also indicate with grunts, grabs and reaching what the problem is. But it's super cute.