It was previously announced that the BBC had commissioned a new series of the Doctor Who spinoff, in partnership with US network Starz.
Myles told WalesOnline: "To be honest, I am quite nervous and apprehensive but then I still get nervous every time I start a new job and then as soon as I’ve filmed the first day I calm down a bit.
“We’re not sure yet whether we are going to be living in Los Angeles or Canada".
The actress explained that she is still surprised at how popular Torchwood has become in the US.
"[The show] is already very popular in America and I had no idea exactly how big it was until I was in Washington DC and I saw myself on the back of a bus. Weird. It’s got an absolutely massive fan base, it’s been the number one sci-fi show for the past three years out there."
She also revealed that she had not remained in regular contact with co-star John Barrowman.
“I haven’t managed to see John much but we get on so well that as soon as we start working it will be like we’ve been together for weeks.”
The new series of Torchwood is expected to air on Starz in the US and on the BBC in the UK next summer.