Valdes made six birdies on the final nine holes of the 7,251-yard course at Shoal Creek golf club, to lead the 156-player field.
Reeves, 17, of Duluth, Ga., opened with a 68, and defending champion Cory Whitsett, 16, of Houston, was among five players who trailed Valdes by four shots. The others were Pat Rodgers, 16, of Avon, Ind.; Cameron Peck, 17, of Olympia, Wash.; Dashiell Lindsell, 17, of Burlingame, Calif., and 17-year-old Julian Suri of St. Augustine, Fla.
Whitsett is trying to become the first repeat winner since Tiger Woods won three straight U.S. Junior Amateurs from 1991-93 and is well-positioned to be among the 64 who advance to match play after two rounds of 18-hole stroke play.
Other past winners of the elite event for under-18 golfers include David Duval and Johnny Miller.
Only 12 competitors shot better than par.
Valdes, a high school sophomore, stopped in New Jersey for a qualifier following a junior amateur competition in Japan and grabbed the second of four spots. Argentinas No. 4-ranked amateur golfer then returned home for two weeks to Cordoba, also the hometown of 2007 U.S. Open champion Angel Cabrera.
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