Most beginners don't have problem with hearing the beat so much as they do in finding the one beat. If you can't find the one beat you will never figure out if it is 4/4 , 3/4, 6/8 or whatever, timing. Start with something easy, not a rumba with strong beats on other counts. Get a 4/4 timing song with a very strong one beat. Have him find the one beat and count it. Once he can do that, try a waltz with a strong one beat. After he is successful at that, then start adding the more difficult ones like a waltz that doesn't have a strong one beat, or one where the one beat is not primarily percussive, or maybe a Viennese waltz, which will throw him the first time he tries to count it. After this basic stuff, then try the harder ones. It's like dancing, the first dance you learn is not samba. Start with the easy stuff.
Remember the best place to practice this is while you are not dancing. There are too many other things to think about while you are dancing, other than trying to learn how to count music.