Fill very large bowl with ice water. Bring large stockpot of water to boil. Plunge 2 lobsters headfirst into boiling water. Cook 3 minutes (lobsters will not be fully cooked). Using tongs, transfer lobsters to ice water to cool. Repeat procedure twice more with remaining lobsters. Using heavy cleaver or large knife, immediately cut each lobster lengthwise in half.
Remove intestinal tract and rinse away green tomalley. Crack claws; remove claw meat.
Place claw meat in body cavities.
Preheat broiler. Arrange 6 lobster halves, meat side up, on each of 2 large baking sheets.
Brush lobster meat generously with some of melted butter. Broil 1 sheet of lobster halves until meat is just opaque, about 3 minutes. Repeat with second sheet. Arrange lobster halves on platter.
Drizzle remaining butter over.
Spoon rice, then lobster meat and salsa onto warm tortillas. Fold up tortillas and serve with lime wedges.
Warm tortillas in an ungreased skillet over medium heat, about 1 minute per side (do not brown). Stack them on a plate, and cover with plastic wrap.
