Trim and discard fat from tri-tip. Rinse and pat dry, then sprinkle with garlic salt and pepper. Lay meat on a hot oiled grill (you can hold your hand at grill level only 1 or 2 seconds). Cook, turning as needed to brown evenly, until a thermometer inserted in the center of the thickest part reads 125° to 130°, about 20 minutes. Transfer the meat to a cutting board and let rest 15 minutes. Cut meat across the grain into thin, slanting slices. Serve with pinquito beans and fresh salsa.