To quote Sofia Vergara herself:
"I go out to a mall or restaurant and when somebody hears me they'll go, 'Oh my God, it's your real accent'. I tell them, 'Yeah, I guess I'm not that good an actress!'"
Still, she admits, her comedic instincts may, at times, cause her to emphasize certain pronunciations
"I do make the accent a little stronger."
"I understand English; I read and write English perfectly, but the accent won't go away."
"When I moved to L.A. and I wanted to act I did want to work on my accent... so I hired a speech coach. He was super-expensive."
"(I spent) hours and hours, because it's not like you can do it one time a week; you have to do it, like, five times a week, three hours a day... It was the money most thrown away (sic). I got worse. Look at me now."
(Note: Just like Gloria, the character she plays, Sofia Vergara was born and raised in Colombia)