On the Capoeira front, my understanding (from conversation & research, not from direct experience), is that it's much like real, old-school TaeKwonDo. The fancy stuff is for practice, or when you're playing, or when your girlfriend is watching.
In conflict, it's taking that body that can kick with power while in a handstand, and using it to power a solid hip-level front kick, or headbutt, or to drive a machete or stick as far into your skull as possible. Train hard, fight easy, right?
In terms of what to do if your leg is grabbed, my advice depends on their position. If they had to bend over to get it, put pressure on the back of their head. Robs their power and forces them to concentrate on staying upright. Then stomp down to free your leg. Wrestlers get out of single-leg takedown just like that allatime.
If they're upright, the best advice has already been given. Bend your knee to reel yourself in and do something horrible to the face. Once you're in close, stomp down just like in the above idea.