My first partner and me went directly to a milonga after oour very first workshop. While I was sent back to tango class for one year and an half, for her it all went very nicely and she started to go to milongas every night she could. Learning curves are different, you don't have to wait for him for another two years before he's ready. And by going right now you will see what tango looks like in your neck of the woods, the milongas, the community, possibly the cliques. Maybe you wont like it at all and will want to switch to another dance. Then better now than after two years of hard work for him.