The sixth-seeded Spaniard posted a 4-6 6-2 6-3 victory over his American opponent, dropping serve twice in the first set but then not facing another break point throughout.
"It's the first match I play outdoors," said Lopez, who converted five of his 14 break-point opportunities.
He added on www.atpworldtour.com: "After Australia, I went to Davis Cup and to Memphis, so I was month playing inside which is so different.
"You need a few days to adjust to conditions, but today was a pretty nice day to play. I didn't play my best, he didn't play his best, but I'm happy to go through."
Lopez will face Adrian Mannarino in round two after the Frenchman overcame American wild card Jack Sock 6-4 6-2 in Monday's only other main-draw match.