On May 5, 1999, at 1950 hours Pacific daylight time, a Beech A36, N6034X, owned and operated by the pilot, collided with an airport sign after landing at the San Diego International Airport, San Diego, California. The airplane was substantially damaged, and the commercial pilot was not injured. Visual meteorological conditions prevailed at the time, and no flight plan was filed for the flight that was performed under 14 CFR Part 91. The business flight originated from Riverside, California, about 1910. Airport officials reported that after the pilot landed at dusk on runway 27, he made a 90-degree northbound turn at taxiway intersection C4. Thereafter, while proceeding at less than 5 miles per hour, he again turned right, entered an oval area short of the desired taxiway, and collided with a runway sign. The pilot indicated to responding officials that the collision occurred while he was looking at instruments.