Do I admit to this...
I used to dance for my University, both Modern Ballroom and Latin.
My only regret was not trying it earlier and having longer to compete. It's fun and yes you can use it when you go to weddings etc. as it is nice to be able to do a few dances properly.
Jive is probably my favourite, a lot of fun and has the highest impression/skill at social gatherings like weddings. Waltz and social foxtrot are probably very useful for occasions. Rumba can look look a bit sleazy and I' not a Cha fan. If you really get into then learn a really good Tango with the missus then you can really impress and make the other women swoon and look disappointingly at their partners.
Starting out it is really hard (well it was for me) to pick up the steps when the instructor is going through them all quickly. It is something you learn to get better with as you see similarity in the steps and no longer have to use all your concentration moving the right foot.
Salsa and Samba are probably the hardest for me to pick up. I blame being a rigid white guy and not some sexy latin stud with fluid hips.