Mitch Glassman led the Division II Mustangs (1-1) on an 11-play, 77-yard scoring drive capped by a 5-yard touchdown toss to Michael Ball to cut the lead to 14-7.
Ross Dwelley had 10 receptions for 123 yards and a score for the Toreros, and Riley caught five passes for 115 yards and two scores.
Armstrong finished with 109 yards rushing and two touchdowns for San Diego, which had 459 total yards.
Glassman threw for 297 yards and two touchdowns, but was picked off three times. Xavier Ayers had 9 catches for 132 yards.
AP College Football website: www.collegefootball.ap.org