The 27-year-old, who completed a move to the club on Tuesday, has also admitted that he is hopeful of being involved against the Newport-Gwent Dragons in their next league clash.
"I'm don't know if I'm going to be involved or not, but I'm looking forward to getting straight into the team and getting some game time," he told reporters.
"I'm very pleased to be back in the Premiership after a few years. It's exciting times for London Welsh - it's a club with a lot of history.
"I'm very excited about the squad; everyone has the goal of retaining the club's Premiership position. I'm looking forward to the challenge and trying to add something to the team over the next four months to ensure the club's Premiership place for next season.
"I've been following the team since I made the decision to come and they've been doing really well. They've surprised more than one team and hopefully we can keep doing that."
The Argentine has previously played for London Irish and Harlequins.