Should I Start Learning Leg Locks?
Leg locks have a reputation across jiu-jitsu as something of a dark art, something that is meant for only those who are willing to play a little riskier than everyone else. The IBJJF and most gym cultures back this up by making any submission below the waist (besides the straight ankle lock) illegal for lower belts, only adding to the mystique of the lower body. So, should leg locks be this regulated? When should a grappler start conquering the lower half of the human body?
How much danger can you do with a leg submission? Well, about as much as you can do with any other submission. A joint lock like an armbar or a wrist lock will always carry risk if the person doesn't tap (the phrase "tap or snap" isn't a lie!), and if it adds a twist? Then you need to really apply and defend with some care. Even a choke, probably the 'safest' way to tap someone out as far as damage goes, still carries the threat of choking someone unconscious, or even worse if you keep going.
A leg lock doesn't add any magic threat that an upper body submission doesn't have already, so learning how to responsibly attack and defend yourself below the waist is something that any white belt can start doing if they have proper supervision. Just like with any move, find someone who has experience applying it, get their guidance, and practice with a training partner you trust. Your knees and ankles may have a range of motion that is a little less intuitive, so you'll have to go very incrimentally, learning when it's time to roll and move and defend, and when the fight is over.
So, when should I tap out to a leg lock? Easy answer, as soon as you feel like you should. If you haven't had much experience with reaps and heel hooks, then your best bet is to defend until you feel the urge to tap, and then talk to your training partners after about what they were doing and if you could have done anything better. With some simple feedback, you will quickly learn your body's limits and you can really start exploring those dark arts of the legs.