Saute the garlic in the olive oil until just softened. In a coffee mill, coarsely chop the coriander and cumin seeds. Chop the jalapenos (reserving all juices, including those in the can). Mix all together. Bone the leg of lamb and cut off any excess or interior fat and silver skin. Break the meat down to the basic muscle pieces. Marinate the meat in the jalapeno-garlic-seed mixture for at least 2 hours or overnight. Drain and grill.